What is wrong with my truck?

Okay so I have a 92 Chevrolet c1500 pickup with a tbi 350 with overdrive, the problem just started a while back and what happens is When I give it some gas 50 - 75% full throttle it sputters, pops but does not backfire and then it will just take off. It usually happens in low gears like going from a stop sign or speeding up from slow traffic. Nothing else is wrong, there is no check engine light, no knocking, no ticking, oil level is good, and transmission level is good. I've replaced the tps sensor, idle air control valve, checked the MAP sensor and it was good. I even cleaned out the injectors and throttle body. I'm kinda out of ideas. It smells like it's running a little rich too. I've replaced the plugs, wires and fuel filter. My rear u-joint seems to be going out it clicks everynow and then but that couldn't cause this could it? Thank you for your opinions