B2300 series pickup misses on acceleration

i have a 2001 B2300 pickup,4cyl,5 speed. it runs great but when you try to accelerate hard below 2500 rpms it jerks and acts like it's cutting out. you can accelerate slowly and it runs fine or anything above 2500 rpms it won't do it. it seems to be the worse around 2000 rpms. i've changed the fuel filter,spark plugs,plug wires and air filter.also cleaned the MAF sensor. 104000 miles on the truck