Greg, if you stump on the accelerator and Idle speed returns to normal it is very possible that you might have sticky throttle linkage (there are so many of them down there). If you want to DIY first remove the air filter housing, then locate the throttle linkage close to and on the right side of the butterfly plate and while the Eng is reving high just disconnect the linkage (a 10 mm open end wrench is the best tool for the task) then check Idle and see if drops down if so then there is a sticky linkage (ball link) some where and you have plenty of lubrication to do. Start by disconnecting all ball links 1 by 1 and apply some anti-seize compound. spraying WD-40 in the joints without disconnecting them will also provide temporary fix. hope this helps.