Fyi, you're not going to gain much if any mpg tuning an lb7. It's not like an lly where you can adjust the vgt to relieve some backpressure, and feee up some hp. You can gain some city mpg with tuning by lowering the shift points and keeping the rpm's down, but this wont work for you with the 35" tall tires. Fixing your rail pressure issues will do more good than anything else will, but in all honesty you probably won't be able to gain but .5-1.5 mpg's with a tune. LB7's stock got the best mpg of any of them stock, but once you mod them, the vgt trucks pick up the most mpg's(I've tuned a few LBZ's that were getting 23 mpg on my econ tune). With bigger tires you can either regear, go to a narrow tire, or go back to stock tires.