1999 4Runner engine hessitation/misfire wduring acceleration

HELP! My 1999 4Runner SR5 V6 recently started hesitating when accelerating after a stop & misfiring under hard acceleration- like when merging onto the freeway or when trying to maintain speed going uphill. On 3 occasions the check engine light started flashing but turned off when I backed off the throttle. It was recently tuned up including new plugs, plug wires, oil change, transmission fluid change, new battery, starter & fuel filter. Could this be a MAF or coil pack problem or something else? Oh yeah, I think the sending unit may be going out as my fuel gage doesnt work properly. I love my Toy & she's always run great til now, plz help meeeeee!