Sponsored

Kooks Long Tube Headers Green Catted High Output 1 7/8''

MustangMental

Well-Known Member
Joined
Jun 24, 2025
Threads
23
Messages
190
Reaction score
106
Location
Missouri
Vehicle(s)
2024 Mustang GT
Got a few questions really thinking about picking up a set of these for my Stang here on black Friday.
1. I saw on Lethal Performance website that these aren't highway legal and you have to sign a disclosure when you buy them. What is that all about?
2. I have a Corsa double H pipe and Corsa exhaust, it looks like both connectors are 3 inch will these slide into each other? Looking to get them professionally installed.
3. My goal eventually is to add a Whipple Stage 1 into it and want to make sure this would be the next step before adding boost. I don't care much about sound, the louder the better (Live in an apartment complex and hate my neighbors plus I work from home, so no cold starts at 7am)
4. Will 02 spacers be required? I was watching a video claiming the o2 sensors get too hot and throw a code so a defoulder is needed. Looking to be able to pass emissions and run without a code.
5. Ignoring the sound issue, this is my daily driver and want to know if this set up will be safe from a longevity standpoint. I don't want to burn the cats out, I do like to drive a lot, but this isn't a track car. Mainly spirited driving and car shows.

Any additional comments are greatly appreciated.
Thank you
Sponsored

 

robvas

Well-Known Member
Joined
Mar 7, 2024
Threads
26
Messages
2,751
Reaction score
2,730
Location
MI
Vehicle(s)
2011 Mustang
These would be great questions for the people at lethal. Why don't you send them an email or give them a call?
 

smurfslayer

Well-Known Member
Joined
Jul 11, 2024
Threads
8
Messages
1,516
Reaction score
1,907
Location
Texas
Vehicle(s)
2017 Raptor
I don't care much about sound, the louder the better (Live in an apartment complex and hate my neighbors plus I work from home, so no cold starts at 7am)
Maybe hold off on the headers and put that money in savings so you can save up for a down payment on a house located in an area with low population density. Then you will have higher quality neighbors you are less likely to hate, and they won't be crammed up your bee-hind all up in your business.
 


Q6543

Well-Known Member
Joined
Dec 11, 2022
Threads
21
Messages
2,191
Reaction score
2,858
Location
Detroit
Vehicle(s)
1993 fox
Huge huge waste of time and money, put that towards your stage 1 whipple kit.

Advice given by someone WITH both headers and a whipple fyi

If you're not going off-road don’t bother with headers and if you’re not going stage 2 you don’t want too either.
 

Junkyard Dog

Well-Known Member
Joined
Jun 3, 2025
Threads
54
Messages
2,563
Reaction score
2,067
Location
Georgia
Vehicle(s)
2024 Dark Horse
Huge huge waste of time and money, put that towards your stage 1 whipple kit.

Advice given by someone WITH both headers and a whipple fyi

If you're not going off-road don’t bother with headers and if you’re not going stage 2 you don’t want too either.
What does the off road part of the comment mean?
 

Steve@Lethal

Well-Known Member
Diamond Sponsor
Joined
May 11, 2023
Threads
71
Messages
225
Reaction score
47
Location
Wellington, FL
Vehicle(s)
18 Saleen Yellow Label
Got a few questions really thinking about picking up a set of these for my Stang here on black Friday.
1. I saw on Lethal Performance website that these aren't highway legal and you have to sign a disclosure when you buy them. What is that all about?
2. I have a Corsa double H pipe and Corsa exhaust, it looks like both connectors are 3 inch will these slide into each other? Looking to get them professionally installed.
3. My goal eventually is to add a Whipple Stage 1 into it and want to make sure this would be the next step before adding boost. I don't care much about sound, the louder the better (Live in an apartment complex and hate my neighbors plus I work from home, so no cold starts at 7am)
4. Will 02 spacers be required? I was watching a video claiming the o2 sensors get too hot and throw a code so a defoulder is needed. Looking to be able to pass emissions and run without a code.
5. Ignoring the sound issue, this is my daily driver and want to know if this set up will be safe from a longevity standpoint. I don't want to burn the cats out, I do like to drive a lot, but this isn't a track car. Mainly spirited driving and car shows.

Any additional comments are greatly appreciated.
Thank you
1. So anything that is not what came on the car that was from the dealership new, has to have a warning like that. You don't have to sign a waiver. We WILL NOT ship them to California though.

2. If you get the factory connect, it will line up with your stock clamps. I recommend this incase you ever want to swap out to a different catback.

3. These are the way to go with wanting a Whipple. The Green cats are designed for boost.

4. The rear spacers aren't required but helps mitigate the chances of a CEL.. You are slowing the air speed down.

5. The GREEN cats are designed for the extra heat produced by boost and will last awhile. Just note that like anything, heat can destroy over time. But I have seen plenty of people with them with no issues.


If you have any other questions, please feel free to give me a call or PM.
https://www.lethalperformance.com/k...2026-mustang-gt-dark-horse-5-0l-1151h432.html
 
OP
OP
MustangMental

MustangMental

Well-Known Member
Joined
Jun 24, 2025
Threads
23
Messages
190
Reaction score
106
Location
Missouri
Vehicle(s)
2024 Mustang GT
1. So anything that is not what came on the car that was from the dealership new, has to have a warning like that. You don't have to sign a waiver. We WILL NOT ship them to California though.

2. If you get the factory connect, it will line up with your stock clamps. I recommend this incase you ever want to swap out to a different catback.

3. These are the way to go with wanting a Whipple. The Green cats are designed for boost.

4. The rear spacers aren't required but helps mitigate the chances of a CEL.. You are slowing the air speed down.

5. The GREEN cats are designed for the extra heat produced by boost and will last awhile. Just note that like anything, heat can destroy over time. But I have seen plenty of people with them with no issues.


If you have any other questions, please feel free to give me a call or PM.
https://www.lethalperformance.com/k...2026-mustang-gt-dark-horse-5-0l-1151h432.html
I plan on going these
Kooks 1-7/8" SS Headers & H.O. GREEN Catted Connection Kit (2015-2026 Mustang GT 5.0L / Dark Horse) - 1151H442
 

25Raptor

Banned
Banned
Banned
Joined
Aug 26, 2025
Threads
7
Messages
103
Reaction score
63
Location
Miami
Vehicle(s)
25 DH
Maybe hold off on the headers and put that money in savings so you can save up for a down payment on a house located in an area with low population density. Then you will have higher quality neighbors you are less likely to hate, and they won't be crammed up your bee-hind all up in your business.
Who said his neighbors were low quality whatever that means. Because they live in an apartment they’re low quality? 🤷‍♂️ Once again “The counselor” is reading into things with a boatload of prejudice I might add. Giving personal advice clearly out of the scope of the thread.

Being a Black Fellow I know all too well about people who speak like that. Been putting up with people like that all my life. People should be careful who they insult, cause you never know who you’re talking too, get my drift. Lots of people have lost lots of stuff over prejudicial comments.
 
OP
OP
MustangMental

MustangMental

Well-Known Member
Joined
Jun 24, 2025
Threads
23
Messages
190
Reaction score
106
Location
Missouri
Vehicle(s)
2024 Mustang GT
I have decided to not buy the headers! Doing the math, 3k for headers 1k+ for install then another lets say 8.5k for supercharger when on sale and another 3k or so for install thats 14.5k+ for boost when I could just get a twin turbo set up for 8500 some fuel injectors and fuel pump maybe do the install myself.
 

smurfslayer

Well-Known Member
Joined
Jul 11, 2024
Threads
8
Messages
1,516
Reaction score
1,907
Location
Texas
Vehicle(s)
2017 Raptor
3. My goal eventually is to add a Whipple Stage 1 into it and want to make sure this would be the next step before adding boost. I don't care much about sound, the louder the better (Live in an apartment complex and hate my neighbors plus I work from home, so no cold starts at 7am)
Who said his neighbors were low quality whatever that means. Because they live in an apartment they’re low quality? 🤷‍♂️ Once again “The counselor” is reading into things with a boatload of prejudice I might add. Giving personal advice clearly out of the scope of the thread.
I like the way the Mustang sounds too, but not without some kind of sound deadening. I've lived next to that. @MustangMental put it right out there he's in an apartment complex and hates his neighbors. Ok, I get that, but my overarching point was maybe a new, loud AF exhaust isn't the best answer. Maybe a better answer is to put that few thousand dollars away and keep adding to it for a better place to live.

Being a Black Fellow I know all too well about people who speak like that. Been putting up with people like that all my life
I'm not sure what you're trying to get across here, so please elaborate.
People should be careful who they insult, cause you never know who you’re talking too, get my drift. Lots of people have lost lots of stuff over prejudicial comments.
This I very much do understand, and quote back for moderator staff and any subsequent reference needed. You know, just in case someone loses some stuff.
Sponsored

 
 








Top