Alceration problem

i have a 1987 Chrysler Fifth Avenue 318 904 transmission. I replaced the fuel filter and pump, the timing chain, water pump. I had a new battery, new starter, and a rebuilt transmission. When I'm stopped and I go to give it gas it loses power to the acceleration, then after a quick second it picks up and it drives fine. It only does it once in a while or alot sometimes only when I'm at a complete stop.