I replaced all of my exhaust with 3" DP, test pipe, and 3" exhaust and had check engine light. I put an MIL in and everything was fine, but I wanted to see. I put a 3" high flow cat without the MIL and the car only lost 6 horsepower to the wheels and passed the GA emissions test. Much more better.

 

This is good to know and helpful.

Thanks for the responce bud.

 

Could someone here measure all stock exhaust diameter?

pipe, inlet/outlet flange diameter--downpipe catalyzer and cat back

thanks

 

i got 2.5 downpipe and hf cat for sale.....its from ultimate racing.....used for 3months ,,,,,prefers pick up....nyc

 

Plus lower EGT's and quicker spool. The top end really comes alive with a straight pipe.

 

cats is more like intake air filter right?
i wanna get rid of restrictive air fitler out.... even k&n fileter is a restrictive ,,,,

 

Much more better?

 

If you keep stock cat, go with HKS DP which is 2.5" then go with a 3" catback. You'll go from small to large. If you go for a difference in diameter, that has better flow.

 

No, the "cat" or catalytic converter is part of the exhaust system and is emissions related.

As for the air filter, a K&N should be fine. I know many people using them and I use one in my 1g Talon.