Well, the first thing you want to check for is:

1. Vacuum Leak. Sometimes it can be difficult to locate the broke hoses, Check the rubber hoses that connect directly to the intake manifold. Well, the best way to do this remove a vacuum line and block its passage with a finger. If the idle drops down, then you have found your problem. Also check the gasket between the intake manifold, and the air ducts between the throttle and the manifold it'self, you may have issues on the intake manifold gasket as well.
2. Check if the throttle is completely released.
L8r bro.