hesitation when accelerating

i have a 94 toyota 3.0 liter v6. When starting out in 1st gear then through 2 3 4 when not on the gas hard there is bad hesitation. When in higher rpm it seems to run fine. It starts awsome idles fine. Just when your your not on the gas hard is the problem. I've changed the plugs and wires but no change. i've been told so many things from different techs. o2 sensors, fuel filter,ect. Any help would be great thanx

Check the timing

Check the MAF

Check for vac or intake leaks

Those would be the places I would start. How well maintained is the engine?