Well I got the mower back from the shop Friday afternoon. They said the carb was dirty, so they cleaned the carb and put on a new fuel filter, and this cost $87. I started mowing with it Saturday about 9:30am. It worked great until my third yard about 12:30, and it started doing the same thing it was doing last week. I was just cruising along and all of a sudden the rpms dropped and then the governor would make the rpms go up and down like in the end of the video. After a few minutes of idling up and down it smooths out. I let it sit for a few hours while I used my walk behind and tried it on another yard and it did it again after about ten minutes. So I'm taking it back to the shop Monday... anyone have any thoughts on what could be causing this?