Hoping someone here can help, because nothing else has...

154,000 miles on vehicle. Regular oil changes. Nothing but highway miles. Now the car has almost NO power and stutters/stumbles until 3k rpm, then explodes with power like a rocket up to cruising speed. When trying to pass another vehicle however, the engine revs up like normal (3k-4k rpm) and the transmission shifts down, but it feels as if no power is actually making it to the wheels because the speed does not increase. This same problem happens when driving up hills. Yet again though, if the rpms drop below 3k, the car stutters/stumbles. Car operates absolutely fine when not in gear, and seems to shift like normal (no hard shifts, erratic shifts or tardy/extended shifts) Checked the fuel pressure, and it is within range. Replaced plugs/wires, fuel filter, EGR valve, cleaned throttle body, replaced Body Control Module.

ANY help?????!!!???

EDIT: Checked Tranny fluid (stupid sealed transmission BS) and it was up to the drain plug.

 

Automatic?

 

4 speed auto with O/D