Grasshopper 721 surging

I have a grasshopper 721 3 cylinder kubota gas engine and it will run like a champ for about 30-45 minutes then it will start surging. You can turn it off for 20-30 minutes and it will run for another 30-45 minutes and start surging again. I have replaced the fuel draw tube, filter, and fuel lines from the tank to the fuel pump and nothing has helped. Is this a fuel solenoid issue or something else? Thanks in advance for any help.

Post all numbers from engine, thanks.

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Fresh high octane gas, oil, spark plugs, air filters.