lol question answered. i have an ivey tune at the moment. trying to see what i should do next. car has a mbc and a ivey tune.thats it. i want to do a turboback but there all to much money and way to loud.i figured stock exhaust 2.5" is good for some power. 3"dp,cat-2.5" cat back. ive seen a few people using stock exhaust. thanks for not ******* the topics though guys dont plan on draging the car. but i would like to have some fun (its an mr so ive been good on the tranny ect. i shifted kinda quick before the rear end almost kicked me in the ***)

 

Let me ask you a question about emissions in your area.

Do they just do an OBD2 scan or do they actually put you on a dyno rolling sniffer test?

If all they do is a visual and/or obd2 scan, then you can do the following to be stock quiet and not worry about emissions fines.

-3" downpipe
-Cat looking test pipe
-stock cat-back
-o2 non fouler (to not trigger CEL light for no cat)

Your car will be as quiet as stock and you will pass visual and obd2 scanned emissions testing. This should be a good enough setup to run 117 mph trap speeds, at least thats what a member did with a similar setup. I forgot his screen name.

Here is what the catalytic looking test pipe looks like. And its stainless steel construction or you can buy non stainless steel versions.

http://www.siliconeintakes.com/produ...1bf3ab9d160486




To answer your question, the stock catalytic converter is too restrictive. If you still want to run a real catalytic converter then I suggest you get a MILspec one for maximum performance. But just remember sometimes the high flow catalytic converters do not pass emissions testing on dyno roller sniffers.

 

On 91 octane, I have a problem with keeping detonation under control with the stock cat above ~18 PSI up top.

Drop the cat and it will handle higher boost without a problem.

On 93 octane or better, you might get 12.0, but I don't think you're doing it with 91.