Small Engines (Lawn Mowers, etc.): uneven idle, lawnmower, solenoid

Question
I have an 13 HP MTD Tecumseh OHV130, 206801A (E).  Engine runs great at low to mid throttle.  When I move to high throttle engine runs uneven and sounds like it is going to explode.  Sounds like engine could be backfiring very quickly as well.  Engine used to backfire when I shut it off but this stopped.  I know very little about engines besides routine maintance.  Appreciate your advice.  Thanks

Answer
there are a couple of things this could be one that I would start with is clean the carb make sure your air cleaner is clean because if that is dirty that will kind of flood you out and then if that doesn't work you may have to adjust your governor if the lawnmower screams when it is at high idle most engines to backfire when you shut them off unless it comes with a afterfire solenoid thanks let me no how you make out