Ok I searched and got some answers but not everything was answered. So My car is odb 2 and it has a test pipe, no cat and a big loud muffler. I have a cel because of the 02 sensor that should be connected to the cat I assume. So I took it to mienike and they said I can get fined for having a test pipe and no cat.... I am in NY. SO my ? is does a test pipe give you more performance than a high flow cat? Would putting a cat make it less noisy? Alot of my friends said if I had odb1 id be ok but since its odb2 i got to pay the dude at the gas station 75 to do my inspection because I wont pass either way. So is the test pipe benefical? Is there any way I can install an 02 sensor or simulator somewhere to make the cel go away? I think my car is running rich because of this too.... Thanks for all the input guys

 

having a test pipe=more noise. period.

the cel will come from the 02 sensor, yes.

 

A good sized cat will flow very well, and won't impede flow much at all.
Carsound 93505 is 2.25"
93506 is 2.5"
http://www.team-integra.net/se...ID=24
SMSP uses either of those above for the majority of the systems he builds.
The ones above have about 340cfm of flow whereas a stock cat from an integra has about 218cfm. Test pipe has about 407cfm of flow. Thats not that much cfm to me to be out of compliance with smog laws. I'm using the 93505 w/o issue.

 

If you're NA then taking off the cat will not yield much power at all and just makes your car loud as hell.

It would make a big difference in a turbo car where exhaust flow is more critical.

In the end it's probably best to just put a cat on there. Not sure about NY smog laws but theres almost no way you will pass smog in CA w/o a cat.