I have a new Sierra with a 5.3L motor, 6 speed tranny, 3.42 gears, Goodyear Eagle LS-2 27555R20s, custom tune, true dual exhaust and a K&N CAI. Ive put it in 2wd, disabled the trion control and StabiliTrak by pressing the button on the dash, manually put it in 1st, pulled the ABS fuse and put it in tow assist mode but it refused to spin the tires even a little. Itd only rev up to around 2000 rpm while pressing the brake and gas. The throttle response is shit and the truck is just plain gutless until it hits 4k RPMs.\rbr\rbrPerformance upgrades:\rbrTruckExhaustKits.com\rbr2.25 Aluminized Steel Dual Exhaust Kit\rbrEbay.com\rbrFlowmaster Super 40 Series Muffler \rbrDual Inlets 2.50, Dual Outlets 2.50 \rbrAutoAnything.com,\rbrK&N 77 Series Metal Intake Kit \rbrDiablewtune.