A friend of mine has a G35 and replaced two of his four cats with "high flow catalytic converters" are these available for the S2K ... all is see is talk about test pipes... if these are the only option... what kind of HP gains are people seeing?

I have HKS exhaust and AEM V2 intake just FYI.

 

I believe the car has high-flow like catalytic converters stock, hence the jump straight to test pipes for power increases.

 

Yup, stock is a nice high-flow unit. An upgrade would be a testpipe.

 

You already have a high flow cat.

 

ok then... next question... what kind of gains can i expect from a test pipe and is there a significant noise increase??

 

gain +/- 3 WHP,slight noise increase,no drone.

 

The 3-5whp gain is magnified as you build on your exhaust system. Once you have a quality header and cat-back, the test pipe will probably gain closer to 6-8whp in theory compared to the stock unit.

 

Optimistic.!!!

 

Random Technologies does make a high flow cat for our car. It is a 4" model. I sent them my cat and we found out that it flowed as well as any they had in production so they made one that flowed more.

If you want to keep your car street legal Random is the only real option I know. By real I mean tested to actually flow more than stock.

 

There is an old old post, probably two years old at least, that had numbers testing both our stock cat and other aftermarket high flow cats. Our cat outflowed all highflow cats and equalled random technology. I'll try to search for it but I can't use the search function very sucessfully.