Had a Flowmaster Series 40 Delta Flow installed yesterday in my V6 and what a difference...now THAT'S an American car sound! Definitely some increased interior noise but well worth it given the low rumble (but far from obnoxious) outside. It may have boosted the hp but I'm not certain; may just be my imagination and I'll give it a couple tanks of gas to see if mileage increases as some have suggested. Regardless, it's a very worthwile, relatively cheap mod. and one I'd recommend to any V6 owner.