Have replaced IACV, TPS, AND MAPS...CAR CONTINUES TO REV UP AND DOWN BETWEEN 1500 and 2500, RPM. RUNS GREAT WHEN ABOVE 30 miles per hour. Only runs rough when in neutral or idling at stop...any suggestions? One mechanic told me it was from a manifold exhaust leak...is this possible?

 

what car, trim, motor, mods etc etc etc. not all cars are the same.

 

How did the mechanic came to the conclusion of a leak manifold?
What test was performed?