Thats due to your truck having 4 catalytic converters. 04 - 05 4 cat systems sound pretty decent with straights i'll give them that.

 

Why do straight pipes mean a loss of low end torque? And if you add a x-pipe, will this bring the torque back up to what you started with?

 

I don't have any low end torque loss, and im running 2.5" true dual straights with an x-pipe turned out lightning style with 3.5x18 tips. Watch my vids if you want to hear it, mine only came with the 2 cats because it was built late enough in 05. And yes that is my truck breaking traction with 10ply 265/70/r17's (50lbs each)

 

I am running a IMCO glass pack on my 05' with the 5.4 and love it. I wanted to keep the stock look but give it that nice deep tone and not have it annoying in the cab. Alot of people say that it sounds like a new Mustang GT when i get on it.

 

i have 2.25" true dual straights with an x-pipe on my 08 f150 5.4L. deffinetly not as loud as one would think it would be. it has a nice tone at cruzing speed, and good volume when i pass people. i dont think is anoying at all, and people tell me its not to loud, just makes a good sound.