when my 1200 nightster xl is driven on the freeway for longer than 40 minutes (approx), and the throttle is released to slow down and or stop- the engine stays revved up for 30-50seconds before idling to the speed im traveling or to the nuetral rest if the bike is stopped. Its got 7,600 miles has been in for all its services prior to the problem starting, since it has started ive taken it in had it hooked to a computer and the cables checked. The cables were fine and no error codes came up. i have since checked with two other hd service departments and none of the techs had any idea what is causing this. Any ideas?