Problem with surging

A buddy asked me to winterization his 06 John Deere x300 with a Kawasaki. I asked him to starting it to reach operation temperature. I noticed at slow rpms the engine was surging but fine at high rpms. So, I sprayed some seafoam in the air intake while at low rpms and the surging stopped but only while I was spraying. Once I stopped spraying the surging came back. I gave a few more quick burst of sea foam then sprayed until it stalled out. Let it hot soak for 10-15 minutes and restarted. After the white cleared the engine is now surging at all rpms. Did I or sea foam make matters worse. I read on here it might be a vacuum leak?
I then fogged the engine, changed the spark plugs, put in new air filter, changed the oil and filter and installed a new fuel filter. I did notice the plugs were out by.005-.007 inch. So I properly gapped the new plugs, sprayed fog oil in each cylinder and installed those. And the fuel filter was quite full of debris. Oh, I forgot to say that before I sprayed the sea foam we drained some oil out and put in marvel mystery oil and put in 3 oz of sea foam on the gas tank with 3 gallons of fresh gas.

Thanks,
Tom

The surging stopped because the engine was burning the propellant in the seafoam .
Your fuel level is too low or the idle fuil circuit is blocked or the air vent to the float bowl is partially blocked.
To clean these areas you need to pull the carb, and take it apart.

Stay away from the seafoam. I have never had it make a engine run better. Always runs worse.
Get some high mileage injector cleaner. Add it to the gas and run it for awhile.
Works when others say you must pull the carb and clean it.
I now add it to my gas in everything once a month.