Rep Power: 741

it's a weird problem, i fixed up all the spark plug, wire and coils, and just had a oil change and coolant change. the car , 1996 camaro 3800, when i accelerate in moderate, the rpm somehow stays at 2k and 3k for a second, then jumps up, there's no backfiring, no noise, the rpm just wont go higher for that one moment, if im on the highway then it's all fine, only when im local that the rpm does that, and it significantly reduces the acceleration speed, does anybody have any clue what might be wrong ?