I had the TPS replaced under recall a year or two ago, however its my understanding that they don't last forever. Some bikes have had multiple TPS', etc.
Since the problem goes away (for a while) after power-cycling the bike, I have a hard time believing that the problem is a varistor.
My bike has had some really strange symptoms lately. I've read the symptoms of a bad TPS but they aren't *quite* like that.
The bike will occasionally hesitate. That is, I'll be cruising along and it will suddenly act as though I cut the throttle a little. It will do this for a few seconds...