engine problem

i got an 86 fiero GT-my car start fine and runs good when the engine isnt that hot yet. but when it gets to its normal temp-the engine seems like its going to die or is choking when ever i press the throttle body + my RPM gauge goes up and down when ever i press the gas + the engine dies when it gets super hot. I know i got a lil leak on my front exhaust manifold and thats is all. i really need help on this poor lady, i dont feel like throwing her away. thanks

Sounds like a top end mechanical problem. Possible cracked/warped head, blown head gasket, or valve problems.
Does your check engine light come on? If so, does if stay on all the time, or only after the engine heats up?