As the title says, i've notice twice in the last three days where the DISA (could also be the ICV, but I think the DISA) will continue humming/soft buzzing for a minute or over after the engine is shut off. I know normally it will hum for a few seconds then you can hear the valve shut, but this lasts for at least a minute if not two. I tried turning the ignition on and off, locking and unlocking the doors, but nothing would stop it from humming. It eventually stopped on it's own each time. I did some searches, but nothing pinpointed what i'm experiencing. Any ideas? Thanks

Oh! btw, this car did have the DISA replaced at 71,000 miles on Jul '08. IT has 111,000 right now.