You want some back pressure if you want to have any low end torque. If all you care about is high rpm performance, then an open exhaust is probably fine, but for a truck that weighs as much as these do, I think you need to keep some low ends to avoid it just being a dog. Every exhaust mod that I have done that opened things up (high flow muffler, headers, high flow cat, 3" from cat back) all yielded gains only at high RPM. I saw no improvement at low end. That's ok though, becasue I wanted to improve my top end for things like passing power, pulling up steep grades and maintining my speed, etc. It's now as open as I dare go, excpet for maybe a y-pipe upgrade.

 

it'll cost you between 100 - 500 bucks, but you can get some of those electric exhuast cutouts. put it pre-cat and you can either run it straight or through your exhuast (if you have to pass emissions). or you can start out running the cutout closed for low end and open it as you accel for high end. that would be pretty sick.