2007 sportsman 500 EFI reving up to bout 2300 rpms on its own

2007 sportsman 500 EFI reving up to bout 2300 rpms on its own.
Sometimes will go back to normal idle.
Sometimes when you first start it , it will rev up high like ya gave it some throttle then go normal.
Yesterday it just revved up to 2000—2300 rpms on its own, I jammed it in gear and parked it.
Any ideas what to look for???