1993 Toyota Paseo Acceleration Problem

My Car for some reason does not accelerate. it will get up to speed well enough to drive around, but for some reason it feels like it doesnt have its true potential till it goes over the 3 rev. I've changed the spark plugs, spark plug wires, distributor cap, rotor inside the distributor cap, fuel filter, clutch. I know everything works on the car because I just changed the engine and was working fine with my other engine let it R.I.P. So I am stuck not knowing what to do next...