1995 Pontiac Grand Prix Poor Acceleration?

[pack_rat85]

I bought a 1995 Pontiac Grand Prix second hand. Engine has 213k miles on it. 3.1 V6 Changed the Valve cover gaskets to fix oil leak. Transmission had taken a dump, so I replaced it with a trans from a 1993 Grand Prix. Had to replace valve body as well for newer design. There are no lights on the dash and after some Seafoam in the trans, the engine and trans run well. Problem is, that it takes twice as long to accelerate to 60mph than my 98 grand am with a 2.4 4cyl. Changed the plugs and wires. Injector cleaner. New air filter. New fuel filter. Replaced brake calipers. I am stumped. Car cruises fine, just no power to accelerate.
4t60-e transmission replaced with same model. Thinking that its something fuel related as the engine drags a little when the pedal is floored. Not the exhaust system, had it checked.