Toyota Repair: loss of power and hesitation on acceleration., input sensors, fuel mixture

Question
'02 4runner, I have a loss of power on accelleration. The truck`s rpms jump rapidly like it is skipping but the speed increases as well. this only happens when i accell and only after speeds of higher than 40. The truck has been to 2 shops and neither knows what is wrong. One shop suggested the MAF which i changed and no difference and the other suggested fuel filter which made no difference. They stated that when they commanded the truck to suck more fuel that it ran much better. it commonly happens when i try to pass someone at WOT, if i let off the gas it drops back down and then i can gain speed normally. Both shops checked tranny for me and said its fine. thank you for any input

Answer
I assume the check engine light is not on or comes on and goes off, is this correct? Since most failures of input sensors would trigger a check engine light it would make sense that the light came on. If it's a fuel pressure issue then the light may not come on but even then it should since the fuel mixture will be too lean when this problem occurs, so before I try to diagnose this any further I would need to know if the light was/is on and what the diagnostic trouble codes are.