04 vs. 05-06 exhaust

**RoadWrath04** · 04-12-2010, 06:20 AM

ok, this might be a very simple question, but i have an 04 and just purchased a rear fascia w/ insert to switch to the split dual exhaust rather than the same-side dual...i also got a full set of the stock LS2 catback exhaust that came off the same car as the bumper, but is there any increase in performance over the LS1? if not, id rather just go aftermarket and sell both stock exhausts (if i can get anything for them)...

**cammed goat** · 04-12-2010, 06:27 AM

Originally Posted by RoadWrath04

ok, this might be a very simple question, but i have an 04 and just purchased a rear fascia w/ insert to switch to the split dual exhaust rather than the same-side dual...i also got a full set of the stock LS2 catback exhaust that came off the same car as the bumper, but is there any increase in performance over the LS1? if not, id rather just go aftermarket and sell both stock exhausts (if i can get anything for them)...

I COULD be wrong...but I think the 05/6 catback is larger as it is 2-1/2" rather than the 04s 2-1/4". So you are gaining more flow with the conversion.

**RoadWrath04** · 04-12-2010, 10:24 AM

will i run into any compatibility issues going from the ls1 to ls2? was thinking of getting a set of lt headers, then running aftermarket, but the headers would be for ls1, then aftermarket (prob slp loudmouth II) would be for ls2, while deleting the cats...any issues here with compatibility? any suggestions for headers or aftermarket without cats that are good performance and sound?

**cammed goat** · 04-12-2010, 12:35 PM

Well, I have seen when folks use aftermarket mufflers where the mufflers rest on the 04s. They just have pipes fabbed up after the mufflers and run out the back with tips welded on the ends, and they use the LS1 headers. Or, you could run LS2 headers to the center resonator and the LS2 catback. Remember, there are many options you can go with on your car.

04 GTO:
Manifolds to mid pipes/resonators, then mufflers to pipes exiting out driver side rear.

05/6 GTO:
Manifolds to mid pipes to ONE center-mounted resonator to pipes exiting under rear axles to mufflers/tips on EITHER SIDE of rear.

**cammed goat** · 04-12-2010, 12:48 PM

I have heard many good things about Kooks, Stainless Works and PaceSetter long-tube headers. I don't think PaceSetters come with cats tho. The other two mentioned do.

**RoadWrath04** · 04-12-2010, 01:20 PM

wait, will ls2 headers mount on my ls1? i'm lost when it comes to exhaust...ive heard that headers really don't do a LOT, so i was considering leaving it stock (except removing the cats), then adding a cat-back system for ls2 (so it actually is pre-bent to go dual sided exhaust rather than dual to one side like my stock system) i have the 05-06 rear fascia to split them out...i'm just confused dammit

**cammed goat** · 04-12-2010, 02:45 PM

From what other GTO owners have told me, yes, LS2 headers will fit on your LS1. The difference is that the 04s have their resonators in the mid-pipes, whereas the LS2s have one single resonator after the mid-pipes.

If you keep your factory mid-pipes, all you need are pipes to sit where your old mufflers were and get the LS2 cat-back.

**cammed goat** · 04-12-2010, 03:14 PM

This is what you have now:
http://www.modernracer.com/memfeatur...toinsides4.jpg

This is what you need and will have after:
http://image.gmhightechperformance.c...st_install.jpg

**cammed goat** · 04-12-2010, 03:23 PM

http://www.modernracer.com/memfeatur...toinsides4.jpg

Now...see where the mufflers sit? You could get a set of SLP bullets and put them there and run 2-1/2" piping from the mufflers out the back to a set of stock-looking tips. Just one tip on either side.

**derbs** · 04-12-2010, 04:36 PM

Originally Posted by RoadWrath04

wait, will ls2 headers mount on my ls1? i'm lost when it comes to exhaust...ive heard that headers really don't do a LOT, so i was considering leaving it stock (except removing the cats), then adding a cat-back system for ls2 (so it actually is pre-bent to go dual sided exhaust rather than dual to one side like my stock system) i have the 05-06 rear fascia to split them out...i'm just confused dammit

Headers will wake that car up with a GOOD tune. Spintech makes a catback with the split rear setup for the 04 I'll PM you the website.

**RoadWrath04** · 04-14-2010, 09:39 AM

i think the spintech looks like a good setup, and read a lot of the reviews...might just go that route thru maryland speed...now i have a set of stock exhaust sitting here for an ls2 (that i bought from a friend thinking i would just use it to get me by) and my stock ls1 that i'm taking off...starting to look like a muffler shop around my place...

**cammed goat** · 04-14-2010, 03:44 PM

Spintechs sound really nice. Nice crackle at idle and snarls upon accel.

**EZGTO** · 04-15-2010, 08:23 PM

Originally Posted by derbs

Headers will wake that car up with a GOOD tune. Spintech makes a catback with the split rear setup for the 04 I'll PM you the website.

PM me the website too. I'm looking to upgrade the exhaust on my goat in the near future.

Did you look at other cat back systems too before deciding on the spintech? I was also considering SLP or magnaflow. I want my exhaust tips to exit the same as the stock on the 04.

**derbs** · 04-16-2010, 12:21 PM

I had the spintech on my car first but made the mistake of not getting the stainless. So I got a good deal on a SLP loudmouth 1 so thats what I have now love it with the 4k stall. I'm PM you the website.

**RoadWrath04** · 05-11-2010, 07:53 AM

getting car out of body shop tomorrow and then the spintech conversion is going on...got the x-pipe and 4" tips, so i will update once i have pics and some idea of how she sounds...thanks for all the info