Put a full tank of gas in it with a bottle of Dry Gas and a bottle of FI cleaner. Plowed for two days and she ran great. Its officially a mystery!

 

Clean the Idle Air Control Valve. Had this happen on my Jeep Grand Cherokee. Did the same, exact symptoms. Did not throw any codes. Remove and clean, I used some carb cleaner. Fixed it right up. Ended up replacing it a year later, though...