Why do people suggest staying with a stock cat if you have a USDM 4-2-1 header

and upgrading to an aftermarket cat with a JDM 4-1 header? Wouldnt the USDM

header work better with an aftermarket cat as well? I have the comptech 4-2-1

and am debating whether to get a carsound or some other car or just stick with

stock. Please let me know..Sorry, I know it was a stupid question!

 

USDM headers have 2" collectors that will flow with the stock 2" cat. The JDM headers have 2.5" collectors that will need a 2.5" cat or test pipe to flow well other wise it will be restrictive.

-tell

 

So why dont people get an aftermarket 2in cat....do they not make them or are

they just not any better? Thanks!

 

I think is is more simply put you can't use the stock cat with the JDM header with the 2.5" collector and you can use the stock cat with the USDM header collectors. I think is is just that no one wants to spend the money