My Ideal mods are in this order hptuners , converter , longtube's , cam, and hopefully an STS .

I've recently seen about 18.3mpg at about 80 mph

 

thats a little too hard to believe. I now have an 05 RCSB 5.3 and I get 17.5 at 75 so you having a heavier truck with a bigger motor I am calling BS on the MPG.

 

call what you want I'm talking from the avg mpg reading on the dash ? cruse on and tailgate down . I have 1500 ecsb with 3.42's and the L33 don't go buy my screen name, with my hd I couldn't get over 14mpg at 70 lol