2002 High Idle when in gear - Not in "N" - in N 1200 Rpm

2002 High Idle when in gear - Not in "N" - in "N" 1200 RPM. It idles fine out of gear; put it in gear and it idles close to 2000 RPM. Go back to neutral and RPM drops to 1200 again. This does not seem like a vacuum leak. Any thoughts on what this could be. What circuit controls in gear idle speed? A vacuum leak would create a rough idle or low idle all the time - right?
Thanks for all the input. Real strange situation.