1992 Pontiac Grand Am ; Acts up when engine gets hot?

Engine Performance problem
1992 Pontiac Grand Am V8 All Wheel Drive Automatic

My car is doing the weirdest things. It seems like when the engine gets hot, it starts acting up. It's almost like it doesn't get gas. I can floor it, and it sputters and spatters, and then eventually gets a big burst of acc. & STILL won't go. But its only when the engine gets hot. Because when it starts acting up, I have to pull over and wait 20-30mins for the engine to cool down, and its fine again - for about 10 more miles. Then right back to doing the same thing. A mechanic told me it was the engine coils, and I replaced them. It seemed to have done the trick, it ran alot better but eventually went right back to doing the same thing. What could be wrong?