what are the differances between a 4in or 5 in down pipe.. more low end, less low end, with one or the other.. what would be the best way to go...i got an stock 05 5.9L crew cab long bed dully.. i would like to do 4/5in down pipe in to 6in or 7in stacks.. if that makes a diffenance.... thanks

 

Well, anything from an 04.5 ( I believe that was the first model year) had a 4 inch down pipe, and 4 inch all the way back. I've heard that you do not get much gain from having a 5 in exaust until you get around 500+ horses. Best thing to do is get a free flowing muffler, or straight pipe all the way back.

My .02

 

go big or go home 5 inch down pipe running to a set of 7" stacks!!

 

^^^^^ Haha...
True... if you want to put out the $$$$ for a little different sound... I'd do it if I had the money lined up, but on the performance end of things...

It's a personal preference if you are doing it for looks/sound. If that's the case, I'd do it all day long. I'm looking at a set of 6" miters now... comming soon...

 

on my stock truck I lost a small amount of low end when I did my 5" turbo back to 7" single(no Muffler)...it was to loud for me so I put a 51" Donaldson muffler on and gained some low end back...

when I went from stock 4" to 5" no muffler I did not even notice the low end lose till I put the muffler back on....it's a pretty small amount either way.
my .02