I have some kind of engine problem

[GT40 2]

I have a 89 Mustang 2.3L NA with a 5 speed. When I climb hills, and have the gas pedal to the floor for awile, when I start to back off the gas it looses power. It feels like something is sucking power from the engine. And I see some black smoke coming from the exaust. It will only stop if I floor it again or turn off the motor.