I want to do something to my exhaust system to give it a better sound, reduce back pressure and hopefully get a little increase in mileage too. Colorado Diesel has AFE's 4" exhaust kit for $400, which sounds like a good price and they said it is a good kit. I am planning on keeping things in stock form so my question is do I just change to a Magnaflow muffler or something similar, or just change the whole exhaust system. I want to keep things relatively quiet inside for the long trips and that is what concerns me with the 4" exhaust system.
What should I do? Is getting rid of the factory muffler going to give me a considerably better amount of exhaust flow or should I just bite the bullet and change it all.
Sorry so long.
TIA
What should I do? Is getting rid of the factory muffler going to give me a considerably better amount of exhaust flow or should I just bite the bullet and change it all.
Sorry so long.

TIA