I have a 99 grand am and we just put a used engine in. I used all of my original stock accessories on the new engine such as, Intake manifold, exhaust manifold, throttle body etc... . We started the engine and it began to idle between 2000 rpms and 3500 rpms like someone was giving it gas and letting off. I changed the Idle control valve, throttle position sensor and map sensor. I was told to drive it at least 8 miles to reset the idle control valve, didnt work. I checked for vaccuum leaks and didnt find any. If Anyone CAN PLEASE HELP!!! I am begging

lol. please, Help me out guys.
Thank you,
Showstopper_88220, Jaymz