unless you are going to do some major power mods is an aftermarket ehaust system a waste of money? if i am just going to do minor modifications like a edge j/a shouldn't a straight piped stock system do fine? its not what i want to do but i don't want to spend the money for something that won't be any more effective than a cheap solution

If you pull heavy loads, it is worth the money for EGTs. IMO

However, I have not seen reported any significant performance improvement in an "after market" exhaust on a mild tune. Back when I was running a 125 hp Edge hot juice, I ran some 9.1s in the 1/8th with stock exhaust. I then Added the Flowmaster muffler and an AFE Stage II air box, and seemed to average a few 100s better. If that helps you great. Muffler sounds good though, and I love that whistle from the turbo. All that noise is worth the money.
:ro)

FTR, With my current tune, I have run 8.30s in the 1/8th mile with the only change to the exhaust still being that added Flowmaster big block style muffler.

When I get my SD lift kit on, I hope to break into the 8.0s or better, still with that Flowmaster muffler. (may have to open the exhaust up some then)

No performance or mpg difference here. Look good, sound good and more turbo whistle. Same with intake probably......but even more turbo whistle.:D

If you are looking for a big performance gain from a exhaust kit it is not going to happen. What it will do is give a slight increase in power 8 - 10 Hp and lower EGT's. Lower EGT's are good for long life of the engine componets and will allow the use of a performance increaser such as a programmer or inline box to run cooler in all conditions. IMHO if your going to step up the performance any over stock you should replace the exhaust.

While I do not know why, with a lift pump and 4" exhaust (straight), the dyno is showing me 281rwhp now with no tuning, stock airbox. This is up from 246rwhp when the truck was new. Is the dyno lying? Dunno. Others have not seen that large of a gain.

I will do exhaust again on the new truck and see if I get the same increase.