Truck hesitates at high rpm's

It's an old 89 chevy 5.7l. I replaced spark plugs and got an oil change. Now I've noticed it doesn't do it all the time. But when I floor it in second (it's a 3 speed manual) when it gets up to about half throttle it will stop accelerating and hesitate really bad. Possible spark wires, map sensor okay be rotor? Idk what it could be because it doesn't do it all the time. It also misfires once in awhile. Help???

Could be a fuel starvation issue...when was the last time the fuel filter was changed? Easy enough to replace.