No, that really donesnt make a difference to me about the cats. Im still new to the subaru world. i had a jetta vr6 before this so the turbo thing is quite new. Anyways, ive been lookin at the HKS one. What is the difference b/t that one and, just for instance, the helix? one has the bigh opening for the turbo and wastegate, while the HKS doesnt.