I have a 2007 classic 4x4 Silverado Vortec Max.. I have volant CAI, longtubes, 3" exhaust with magnaflow cats and muffler, custom tune HP Tuners, corvette servo, factory 4.10s of course, and i get 18 mpg on the highway with 22x12s on 32" tires. Love my bolt ons.. just installed a tru-cool max trans cooler, and got a 3200 stall waiting on my cam and springs to get here so i can throw it all on! VMax or die!!