Don't really know why it fixed it, but I tried every trick I knew, disconnecting the battery to reset the computer, unplugging all the connections on the throttle body and a few more. As a last ditch effort I turned the key off and back on several times with the engine running, then turning it on before the engine could die. Did the same thing with the kill switch and on the first time back on, the engine dropped down to normal idle and has run perfectly since. Don't know why, but it worked. Must have reset something?????????????