I have searched and read other posts, but everybodies set ups are just a little different, what works for this one, not that one. I am kinda starting out and figured Id ask the guys that have been at this point.
There are alot of options out there for exhaust. I have a set of pacesetter LT about to be installed. Space is an absoulute premium for me as my truck is lowered 4/6. It will have an x pipe. My exhaust questions are what size pipes should I run, thoughts on on mufflers, and what hi flow cats are being ran without blowing them out?

My tune question is (pretty sure I know the answer) do I need it? The mods to the truck are listed below. Nothing has been done internally. Seems like I am forgetting something but cant think of it.

granatelli maf cold air
k&n FIPK
underdrive cank and alt pulley
pace setter LTs
helix tb spacer

 

First things first, go back to your stock MAF sensor, the aftermarket ones that claim hp and all the other bull are completely false and from what ive heard they throw things off when getting a custom tune. Next is go ahead and take the TB spacer off, its also completely useless and does nothing for performance. As far as exhaust goes, i wouldnt recommend anything over dual 2.5" because you wont have enough pressure for anything larger and it will not only hurt performance but also sound like garbage. Depending on where you live you can get away with not even running cats if you can find a shop that will work on it, thus saving you quite a bit of $$$ by not having to buy cats. If you do decide to get some high flows i would recommend magnaflows hi flow cats, im running them on my truck and am very pleased with them. Mufflers i would stay away from anything that is chambered like flowmaster, etc because that will also make you loose some low end. Truthfully if I were you id scrap the idea of duals and run a single 3" exhaust after the headers. I think for the minor mods you have youd be alot happier with a single exhaust and still have plenty of growing room for future mods. Again, these are all personal opinions but I have tried SEVERAL different exhaust on my truck and i havent been truly happy until i went to single pipe. Granted my truck is a 6L and i have a few more mods than you do but single exhaust is plenty for what you are doing.

Zach

 

Stay with the stock cats, they flow good and don't melt up. Run dual 2.5" pipes into a free flowing muffler like magnaflows. And yes a custom tune makes a world of difference.

 

x2 what they said

 

everything he said I back 110%. long time ago, i had flowmasters, and i would lay on accelerator and truck would fall on its face. i switched to a 14" magnaflow and loved it. but it was loud. now i too have my 5.3L with pacesetter lts/ory, with corsa exhaust and turndown after axle, wouldnt have it any other way. i love my single exhaust.

edit: and im lowered as well 4/6.5