People with the hks 30th anni exhaust what kind of high flow cat do you have on or a test pipe. I couldnt get my helix high flow cat to bolt up to my hks exhaust but maybe i just have to play with it a little more. The hks flange at the end of the catback tapers down so the flange is smaller then a 3" HFC.

 

I had used Ultimate racings 3" test pipe with no problems.

 

anyone else?

 

I have a Helix cat bolted to my 30th anniversary cat-back. No problems.

 

Same here, no probs. Make sure you use NEW gaskets!

 

hmmmm, ill take some pics if i have any problems and show you guys what i mean.

 

helix test pipe with no problems