2000 Chevrolet Silverado 4.3 vortec plague

I bought this truck at 89k miles, and in 2 years at 120k miles the problem still persists if not getting worse.
This truck is a Silverado 4x4 5spd with a 4.3 vortec motor.
Since I bought the truck its always had a problem at part acceleration, it always bucks, jumps and loses power, sometimes terribly, sometimes barely noticeable. I've changed the plugs, wires, and dist cap and button several times, changed the fuel filter, cleaned the egr, the maf, changed fuel filter, changed throttle bodies, and nothing to any avail. Recently It's been getting a little bit worse, it's always had a slight miss at idle, but you can kind of feel it now, and when going WOT, in 1st and 2nd it's fine, you can feel it lose and gain power throughout the rpm range, but it does fine. My gears are short due to 3.73s from factor, but when I hold out 3rd at about 4k rpms or so, it dies, and won't go past a certain rpm, when I change out of 3rd to 4th or 5th it misses like crazy, and won't accelerate, actually decelerates, it clears up after a while, but when I let off throttle completely it goes to <200k rpms and will almost shut off. I don't have the courage to see if it actually will.
Any help on this matter would be appreciated as it is driving me crazy, and I don't have money to be replacing a hundred sensors and parts like everyone online says to do.