I just got mine put in. I have a CAI and borla cat back done already. (3.4 pulley, 180 t stat sitting on my bed). Anyways. What did you guys think of your exhaust sound after your Cat was done. I hear a different sound coming from the CAT area. I think it might be an air leak or can you actually hear a flowing sound. I don't know. But I love the overall sound. Nice little power increase. Is it possible that I lost low end torque like with the cat back??????