99 sierra 5.3 auto, if over 1/4 pedal acceleration, engine bogs and barely accellerates. If you ease onto the throttle, it accelerates fine. Tried running gears individually and used tow mode, no change. New fuel pump, msd 8.5 superconductor wires, iridium plugs, battery, and transmission, no change. Got it scanned, random misfire code appears. Told possible air leak but can't find one. I was told that the 5.3 has lots of power, but mine can't even spin 33's in mud. Seems to get a little better when warmed up but still acts up. Going to try fuel filter and regulator next, but gettin sick of throwin money at it and seeing no change. Any help is GREATLY appreciated.