Depends. What else have you done to the engine? A stock 5.0 with a full 2.5" performance exhaust may actually lose power. As for the parts, I've had pretty good luck with MAC (exhaust) products. I've used two of thier catback systems on my GT, and one on my wifes LX. They install easier than any other brand I've used, sound good, and hold up well and I live in New England where there really is a winter season. They get driven every day. I also had the Prochamber, and loved it. Fantastic sound and lots of grunt. It survived more physical abuse than any midpipe should have to, and was still usable when I took it out. I've since had a custom H pipe made, since it was getting tight under there with my mods and it didn't fit anymore. Kept dragging on stuff. I miss it, this H doesn't sound anywhere near as good and I definately felt a loss in power. Oh well. I've heard a lot of crap about MAC headers too, and for the life of me I don't know why. I bought a set of thier shorties from a friend who needed money, and I was hesitant because of thier reputation. It was a good deal and I couldn't pass it up, so they went on the wife's car. I don't know what everybody else did wrong, these things installed like a breeze and have held up great so far- almost a year under the hood. Maybe I just got a good pair, I don't know. I've heard some real installation horror stories, but mine were a piece of cake. Good luck.
