Help… Kohler 7000 series 26HP engine

Alright gents, new to the forum. I need some help from some more experienced small engines people. I have a kohler 7000 series 26HP engine on my Husqvarna 54” riding lawn mower. The engine started surging at all throttle positions a few months ago. It comes and goes as you drive it. I have changed oil, plugs, filter, gas (Idaho non ethanol), fuel filter and fuel pump. I blew out all gas lines and checked the gas tank. I removed the carb (three times) and throughly cleaned it out with air and carb cleaner. I also put seafoam in the gas to see if that helped. My carb does not have an air/fuel screw to adjust carb. The last thing I can think of and have saw YouTube videos about is the spark plug coils. I haven’t replaced those, I’m willing too they aren’t very expensive.

Any help is much appreciated the mower is a 2017 with approx 187 hours on it. I have always used non ethanol gas throughout the life of the mower and change oil and filter every 50 hours and plugs at 100 hours. I mow approximately 1.5 acres twice a week during summer and use it for snow removal in winter ( only a few times).