Berk has a built in CEL fix. It just extends the O2 sensor out of the exhaust stream to prevent the CEL light from coming on. Stillen on the other hand does not have this feature but you can add the bung to extend it out, but that is just more $$$.
I just got my Berk HFC's in the mail and they look great! I will be installing them this weekend. I say you contact Kyle at import parts pro. He was running a group buy and I think it is still going. That best price out there right now! Hurry before it's to late!
Good luck
