start with a quick wind in and out of your idle air screw as wrong adjusment there can cause high idle, count how many rotations it is set at first, check for cable sticking, throttle valve sticking, idle speed to high cable and or screw, what happens when you take the air filter off does it worsen? can you hear the throttle valve slamming back down (clunk) does blipping the trottle get it back to idle?