Brother in law actually gained a little mileage out of it, but probably because he did tune up, cam sensor and fuel pump all in the same week. But Imo, which could be squat, sounds like the cats. Open her up let her breath man. FYI too, most exhaust shops will not touch your system if you have no catalytic convertors on it. So if you cut em off, and try to have straight pipe welded in, they will not touch em! Cost to replace both of his was around $500. I wish I could find somebody to cut mine off and run straight pipe all the way to the flow master, but I just like the sound, lol!