HELP bottom end power loss

[99 shortbox sierra]

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.

[MyTOY]

fuel filter? That should have been replaced with the pump and is
usually the first thing people replace when having a prob. like this.
I've also seen folks with bad cats. have this sympton. good luck

[99 shortbox sierra]

Fuel filter makes no sense though, at idle it revs fine and doesn't miss a beat, also starts fine, i was guessing at the MAP sensor or the MAF sensor.

[plnuout]

I think i know what may be going on, do you have a k&n air filter, or any other kind of aftermarket airfilter with any kind of light oil on it?, if so you may have got a little bit of oil on your map sensor, which a diagnosic tool will not detect. I went through about $ 1100 trying to figure out what was wrong and all it takes is a $2 can of friggin carb cleaner to the map sensor. After you spray down your map sensor it may still be boggy but drive around for a while and it may fix your problem like it did mine. Good Luck

PLNUOUT
Billings MT

[Low-Low-SIERRA]

Hey bro I had the same problem a couple months ago. I ended up spending like $800 bucks and nothing. What ended up being the problem was the Catylic converter it was pluged up and that also ran me like $300 bucks for a dyno.

My truck did the same exact thing you are describing.

[Regalwhiskey]

Perhaps the computer can't handle the tire size. Has the Torque gone south and you need lower gear ratio's?

[99 shortbox sierra]

how many miles or kilometers were on your when the cat plugged up?