Problem of sudden acceleration

I have a ford probe 2.5 v6 24v 1995. 120000 mileage
problem of sudden acceleration. I ask for help.
During rapid acceleration, the engine sound change, poor speeds, it seems like it runs on three cylinders. During the gradual acceleration of the car is going well and the sound is good.
So the problem is in hard acceleration, the engine is choking, change the sound, and loses power
car does not report any error, what's the problem.
Just to draw your attention, when I reduced the gap on the spark plug with 1.1 mm to 0.70 mm in the car behaves nicely with hard acceleration, but stops at the gas constant, and badly at idle. Please if you know what's the problem, please help me.