Why will it not accelerate correctly?

...again, am like a broken record here, it's the EGR valve, what takes exhaust gas and puts it into the intake manifold under decel and/or specific conditions, gets messed up with carbon and frequently has a leaking vacuum control hose~ take it apart and de-carbon it, or buy a new one~

Could be something dealing with the ignition timing. Where it will run good but no power. Vacuum advance if it has one.