I definitely had a gas smell with the cat delete. I sorta' got used to it, but the wife didn't. Was a quite a bit "raspier" as well with some back pressure pops on full throttle lift offs. Not good. (with SW 2" headers as well, stock mufflers). Ended up putting in some hi-flow cats and is perfect now. Still smell a bit, but only if sniffing around and the Mrs. doesn't notice. Didn't dyno with just the cat delete, but lost 3 HP with the new high flow cats put on. Well worth it, but if running higher boost and the resultant increased heat, I put them in so I can take 'em out pretty easily and just a little bit further back since I've heard of a few "burning up"