I am concidering a few different "accessories" for my 1999 5.3 sierra and figured with all the knowledge and good taste that circluates through this forum that you all could help out.
My options are as follows:

1. underdrive pully
2. headers / gut or replace cats.
3. 2in. body lift
4. ford torsion keys and some 2 in blocks out back( stock springs pretty worn out)

Note, i have airaid intake and 70 series flow, (i just want some more power/ better gas mileage) but mainly better MPG. the lift is obviously for looks which also matter, of course.....

Any info would be greatly apreciated. Thanks a lot.... Cory

 

I would get a programmed PCM first. it makes an awesome improvement to the power potential of the truck

 

Out of your list ... I would opt for the headers. They would give you nice gains as long as you don't get shorties. I would spring for TOG's and get them coated by a local shop.

 

get a nelson tune first.........then get your upgrades........they are free for life and will make all your future upgrades work properly......

 

Ok, have you had a body lift before. I suggest never to use them. They ride like *** and especially if you crank up the torsion bars oh man get ready. Just a suggestion becasue I did that on my 97 z71, cranked tosions 2 inch body lift, it's a whole different truck and it sways all over the road. But a tune would be great for your truck. By the way I was running 16 inch wheels with superswampers ssr 285-75-r16.