1991 Chevy Lumina

The car starts right up and runs fine on the highway.
When slowing down right before I stop it lunges forward and is hard to stop. Once I stop and put into park it wants to shut off. I put a throttle position system, a MAP system, EGR valve, sprayed 2 cans of carburator cleaner & 1 can of intake cleaner to clean the intake. When I initially put the MAP system in it ran perfect temporarily then started acting the same way again.
Thanks for any assistance you can provide.