1983 300CD

Car is finally running, idling nicely, and warms up just fine...however, it has almost no power (in any gear) when I attempt to take it out on the road. It just creeps along, takes forever to rev up, and will not climb even a small hill. Once it does rev up, it will typically immediately die when I let off the throttle after the rev up. Also, after it is warmed up, if I rev it up in neutral, it will immediately die when I let off the throttle after the rev up. It starts right back up after it dies. If I rev it up when cold, it does not die.

I've checked all the normal stuff:

1. Throttle linkages are fine
2. No dragging brakes
3. All fuel filters (including the tank strainer) are good.
4. Good fuel in the tank
5. It has what I think are good compression numbers (1-360psi, 2-395psi, 3-405psi, 4-390psi, 5-360psi)

I'm starting to question if maybe there is a transmission issue. Any other thoughts?