My 97 with a 4.6 had the factory exhaust side-exit. I went to a friend who works at a Midas and told him to cut the muffler off and run a pipe back out the same way. The truck sounds awesome but I did notice that it lost some of its *****. So now I was wondering if I could run 2 smaller pipes from the Y-pipe back or does this truck need an after-market muffler to regain some of its umph back. I just want it to have the Lightning side-exit look.

 

What is not understood is the factory system has been optimized.
You just cut a good system off and now see how good it was.
Also it does not involve back pressure since taking the muffler off did not improve the power as you thought it might.
It is a tuned chamber muffler that is the key to the best performance on these truck applications.