Cobb, like all other aftermarket exhausts that are a "direct fit" for the OEM USDM downpipe/cat, has a 2.5" flange and gasket. Cobb's exhaust then widens up to 3" after the flange.

Any "direct fit" exhaust will narrow down to 2.5" because the US flange uses a donut gasket vs. JDM's (and various aftermarket) use of flat gasket (IIRC, they are 3" stock).

My car i went with an aftermarket DP (3") and I had my Cobb exhaust modified with a full 3" flange (flat gasket) to fit.

OP, as others said, what's your goal? Do you mind switching to an aftermarket DP? Even besides the flange issue, do you want a quiet or loud exhaust?

and...welcome to the Subie family!

 

thank you, glad to be apart of it! well thats the thing i have no problem getting an after market dp and as far as lound or quiet i cant make up my mind. my younger brother had a cobb cb for his 06wrx and it sounded sweet. but i like showing off a little bit so ideally loud would be it but the cops here are dicks so cobb might be a better choice. i just cant make up my mind.. overall im looking for sound, quality and maximum performance from it.

 

QFT
I went to the cobb ss exhaust system after getting a "noisy muffler" ticket, before I had a greddy racing Ti-c catback. I love the cobb system. I don't get harrased by cops anymore, not too loud, looks stock. I also had a 3'' flange welded on to mate up to my 3'' downpipe.

 

I hAve a Perrin stealth sounds great and doesn't attract negative attention...

 

This is a video of mine the first race

http://m.youtube.com/index?desktop_u...&v=fn5N66UEsZY

 

Will a 3" exhaust have alot of turbo lag?

 

3" inch exhaust will not effect spool up time (turbo lag). Only mods done to the intake side (turbo, length of intake tubing) will effect spool up.