in my opinion i have owned a 4" and my brother who had 5", there is very little difference if you dont have the power to push out a 5. both are good choice and will accomplish the same thing but the 4in should be easier on the wallet

 

true true.. i just only wanna have to buy one once haha

 

There is NO point... I repeat... NO point where a 5 inch exhaust is "nessasary" or builds more power.

End of story.

 

ive got a 4in down pipe an 4 in mbrp, truck runs just fine with chip an intake an all that stuff. 4 in is all u need, especailly if your not planning on building ur truck to the max. if u want a deeper sound 4in down an 5 in back, but thats all its going to give u is sound. 5 may give u a little longer of a turpo spool time without the fuel an air upgrades, from what ive been told, but to answer ur question back pressure is not an issue. either or is fine just go what you like

 

everybody i talk to says a five is pointless, the 4 is just as good and cheaper, all the diesel shops round here recommend 4, anything bigger is a waste of money they say, you get very little sound difference for the price

 

I'm running 4" MBRP (duals...I like things to look balanced so I wanted two exits ) and it is plenty. A guy I know (Brian Jelich, check it out on YouTube) is pushing 992 HP in his Stroker and he was only running a 4" with a single 6" stack (before the hood stack was installed). So as CSIPSD stated, 4" is good enough.

 

GO 5 inch!!