i have a 3.5 inch straight exhaust..would a 4.5 or 5 inch make it run cooler when i put my foot into it?...also when i get on it i have 0 psi in my fuel pressure.what could i do to help that and by doing that will it kill my fuel mileage?

 

what yr truck and do you have any programmers/pressure boxes any other mods?
0psi at WOT means better fuel pump a fass or airdog etc.

 

you dont mention what year you have... with 3.5 I'm guessing '02 or older. dont go larger than 4" otherwise you will loose mpg. it also sounds like you need a stronger lift pump... FASS or Walbro would be the way to go.

 

it is a 2002 5.9..auto..juice with attitude

 

the juice may be adding too much fuel...hence the 0psi at WOT, thats causing the increased the EGTs.

 

what can i do to make my egt run cooler?...not get so hot when i get on it.

 

How hot is it getting?

Either a 4" or 5" exhaust. You aint gonna lose mileage from one to the other.

Air intake-at minimum a drop-in filter. Dry element, dont use oiled

You definately need a lift pump. You need to address that ASAP. No fuel pressure means the injection pump isnt getting the required fuel it needs. Its lubricated from the fuel, so you dont get fuel to it, your gonna be replacing that soon. Id bet the damage is already done, so be expecting that...

 

if you go to 5" you will loose mileage... heck if you run a 4" straight pipe you'll loose mileage. had a straight thru 30" magnaflow & lost 1.5~2.0 mpg IIRC. The top end was awesome, the bottom end not so awesome (for daily driving). added a aero 4040 where the cat used to be and got back about 1.0 mpg but kept a decent amount of low end (sacraficing top end).

 

You need to fix your fuel press. issue A.S.A.F.P.!! When you do that, I'll bet your E.G.T. issue will go away.

 

How do you lose mileage with a 5" over a 4?" Only thing I can think of (and the same with adding a muffler) is it sounds different so your not in it as much!! Haha

I gain a SLIGHT amount of mileage when I replaced the muffler with pipe, so it was straight from turbo back, through the cat. My mileage didnt change going from the factory 4" minus muffler, to 5" turbo back to 7" stacks, no cat or muffler...each truck IS different though