Just purchased an '06 GMC Sierra, 5.3L Z engine crew cab. Am interested in installing mods that will help with the fuel mileage. I've done alot of reading and research and I'm more confused now than ever. Most mods claim increases, but after reading responses by the users, these appear to be false. I want to install an intake system (K&N or Volant), cat-back system (Magna Flow or Flowmaster) and a perfomance chip/computer (Jet or Hypertech). I'm also considering headers and MAS. Does anyone have experience with installed mods that show any appreciable fuel mileage increase or am I just wasting money if I install these mods? I know these mods will increase hp and torque, but again, I'm more interested in fuel mileage. I'm currently getting about 18.5 mpg and would be happy with 21 to 22 mpg.
Thanks for any response!

 

low 20's are completly achievable with the mods you are focussing on. Only issue is; keeping your foot out of it after you have installed these items. Your truck will take on a whole new personality. Be prepared for more noise though. Not so much with the exhaust, any decent cat back system will free up some horses, I noticed the most increase in off the line torque. Noise will increase with the intake. Some trucks whistle, mine sucked. You could literally here it suck! Sounded like a old 4 barrel when you slammed opened the secondairys. Didn't bother me a bit, but I have heard a number of folks unhappy with the new sounds. So proceed with confidence, just be prepared for the noise though. If you visit a local speed shop, I will bet that somebody there has already done what you are looking to do. Ask them to fire up ther rig so you can hear it.