1997 cavalier 2.4 engine, had problem with engine hesitating. I took it into the shop, they found a vacuum leak to the map sensor and they cleaned the fuel injectors. A couple of days have passed since the work has been done, now noticing that the engine will surge upon deceleration while in park and will idle fine. It only surges while in deceleration mode. Any insight or suggestions as to what may be the problem?