Ok...I have a 1999 Silverado Z-71. I am looking to do some decent priced mods to it. I am looking for the best, and most affordable, gear to mod it up. I want to track down opinions on the following:

Throttle Body Spacer
Exhaust-I want to dual it out
Tuners
Body Lifts
Tonneau Covers
Off-Road Replacement Bumpers

I have checked out a handful of these and really don't have any basis for which are the best, so I appreciate any help here.

Also, I am going to have to gut my audio system and replace it so any tips on how to go about that would be awesome!

Thanks Y'all