1994 Infiniti G20 Has less acceleration or power the more y

This car ildles great, revs great, drives great. But when you accelerate, you can barely press on the pedal because it boggs down and acts like it has no power. When you get the revs up to 4000 or more, it accelerates better. Going up hills it dropps in speed quickly and if you give it more gas it gets worse. The plugs are new, wires are new, cap and rotor are new, air filter is new, fuel filter is new. What gives?