Hello , Had the truck for a while now and Im having a weird problem. It a 1999 auto with a 5.7L engine 110000k , problem only occurs when the gas pedal is floored (at any engine speed) it seems to buck /spit and sputter and not really go anywhere (almost like its miss firing or tranny bucking or cylinders being cut but no codes) > If I lay into it slowly it runs great and strong , It just seems to happen when I put the hammer down , kinda at a lose where to look for a problem . Any input would be helpful at this point .

I would first start with changing the gas filter, see if that helps, I could also be a problem with the cats. Also the O2 sensors should have been replaced at 60,000 miles, they could be giving a funny reading, but not enough to see a code, or there is a code that is not tripping the "SES" light. Take your truck to a shop that has a good OBDII scanner and have them watch the tps, etc. when you floor it.

The truck was given a complete tuneup about 8000miles ago , I just changed the tps , still have the same thing happening, possible torque converter lock/unlock????

The truck was given a complete tuneup about 8000miles ago , I just changed the tps , still have the same thing happening, possible torque converter lock/unlock????
I would check your fuel pump pressure. it might be getting weak. when you first turn the key on its suppose to go up to 65 psi and then maintain around that pressure. if not or low pressure means it needs replaceing.