Kohler engine surging

I have a one year old Husqvarna 24 hp with a Kohler V twing SV725 engine. About a month ago it started surging. I drained the gas and cleaned the carb but no help. So I replaced the carb. Ran great for about two weeks, now it's surging again. I'm running 93 octane, ethanol free gas. I'm at wit's end. Kohler refuses to honor warranty on anything that may be remotely fuel related. They said that any other defect would have shown up before now. I could really use some help on this one.