They flow just about worse than OEM. You probably have an all 2.5" system too right? Was it a muffler replacement only or did you have a new tailpipe bent? If so was it mandrel or smooth bent? If its crimpled then that would be the first source of energy loss.

And also make sure your not overdue for maintainence ( such as new fuel filter, thats one of the first things to check with a little energy loss )

 

yes its stock pipe, just had the muffler replaced and it dumps right out of the muffler under the bed of the truck, when i bought the truck it has some cheesy off brand turbo muffler on it so i put the flow on and since then seems like i have lost power, ive lived with it for years but the thing seems gutless, evenwith the superchip power programmer and the fipk.