Low end lack of power engine hesitation

I have a 1989 Standard Pickup r22 motor F/I 5 speed 4WD.

Truck started recently having a major hesitation on low end going thru 1-3 gearssmoothes out in 4 - 5 gears?

Replaced the fuel filter no help, gave it a tune up with new cap rotor plugs and wires about 15k miles ago.

Can't figure it out
any Ideas would be appreciated
Thanks Mikey58

I would look for a vacuum leak and then a compression test, or if you dont have a compression tester a vacuum check, you should be able to borrow either one of those tools from Autozone. Let us know how it goes.

Nate