The UR cat would be the first choice.

Watch what cat-back you are using, make sure the flange will fit properly...

 

does the UR cat fit the HKS hi power?

 

will the UR cat or random tech and the RMR one fit the Greddy TI and Helix DP?

 

The UR cat is a standard 3" flange. If your cat-back has a universal flange (slotted bolts) and is a 2.5 flange (same size as stock), you're going to have problems.

 

My Helix HFC DID throw a Service Engine Soon lite...thank god I have a code reader/scanner/erase under my seat...

stupid emission controls....

 

that is what i have. fits fine. going to replace it with a UR testpipe though, for no other reason than me and my evo are probably heading over to Korea in a couple months and over there seems the more pollution the better.

 

i have the ur cat and the hks exhaust it fits fine.

 

to the dude with the Greddy Ti Helix downpipe, go w/ the Helix HFC, fits perfect.

 

i have the Works HFC, not sure on its numbers but works great!

 

someone said the 30th ann hi power tapers down to 2.5" when it meets the cat and so i might have a problem fitting a 3" cat? how did you guys do it?

 

I have a WORKS 3" high flow cat mated to my hks 30th cat-back. The gasket still allows a seal, so I have no leaks. Since the flange is pretty thick, I plan on porting out the flange giving it a little taper, so the transition isn't so abrupt.

 

damn, so it does taper, but it doesnt affect the fitment. i guess ill have to a look for a new exhaust.