02 Crown Vic Lx overheats and losses acceleration.

After driving either on the highway or city
streets I feel the car loosing acceleration
and when i come to a top the temp goes up
a notch and as i go it struggles a bit to
accelerate as if it wants to stall but it
doesnt as i keep going it goes back to
normal but the temp keeps going up and it
gets to the point where its all the way up
and it starts loosing power  again
(acceleration) i have already replace the
intake manifold and thermostat. brand new
spark plugs. let me know what you guys
think thanks.