Just wondering what the difference is i will be running a 07gt (supercharged) with headers downpipe, pcm and all supporting mods for either a 3.4 or 3.5 pulley. The car is a daily driver but i have no emissions testing or any thing . so what would be the benefits of a catless down pip. if any at all? what one should i go?

if you dont mind spending the extra money get a catted downpipe. Youre not gonna make enough power on a 3.4 setup to be hurt by having a cat. the only reason i dont have one is because i'm cheap, lol. Plus it smells bad without a cat.

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'05 WRX STi - COBB Stage 2|Invidia DP|3" Borla XR-1|Coilovers|Camber Plates|Swaybars|Endlinks|Bushings|Braces|Anti Lift Kit|DBA4000s|SS lines|
Sold: 06 Cobalt SS/SC, 99 GTP 245WHP/326 Ft-lbs, 06 R6

the difference aint much in performance wise with that pulley...


^^ the main difference... ooo and it will make u cry when ur idling in traffic with ur windows open lol...
last comment i got about my car with another car racing me (behind me)... ""Buddy!! ur car stinks"".. i was like i know
plus it would b a little louder

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Black 06 GP GT
S2 IC, 1.9 Rockers, TOG Headers w/ full custom exhaust, CAI, 104 Autolites, Custom Tuned PCM, 3.3....
And still Working its way up....

cut down on backpressure id say.

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Behold the majestic beast as it strides

depends on how you want your exhaust to sound, too. Seems like you're going the performance-oriented route, so I would say catless or not its your choice, but it wont make much of a difference either way performance-wise...other than backpressure like Daytona mentioned...maybe help you a lil more in the upper RPMs but i doubt it. But if you dont want your car to rasp and sound like ass even worse than what the 3800 motor is notorious for, then keep a cat on there. A lotta people say the exhaust rasp is exclusive to the 3800 but im convinced having a catted exhaust system has a lot to do with how well the rasp is cancelled out. Just my .02

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2005 Pontiac Grand Prix:|SE front|SPO grilles|HPTuned|HUD added|5-button DIC swap|Wizaired CAI|180*|EGR delete|GMPP rear sway|F&R STBs w/DRs brackets|3.29s|HD Diff|7/8" chain|WBS TA's|SD Headers|GenV SSM90 Hybrid(INSTALL PENDING)

i hate the sound of the 3.8 and i own one. blows

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Behold the majestic beast as it strides