Originally Posted by BLM

I would advise keeping the stock cats simply because if you get an aftermarket exhaust you run the risk of having the hissing/whistling noise. I have it and it doesn't bother me that much and the car makes great power. Regarding emissions, idk if a hfc will pass. I just went with a straight test pipe. I'd do a test pipe or leave the cats in. The only way i'll change to an HFC is when ARK releases their HFC to fix the hissing sound from the combo of their exhaust and test pipe.