I have a Simplicity Prestige tractor with a Kohler cv23 engine. The tractor has developed an intermittent miss. It start and runs fine sometime. Other times it has a miss. If I shut it off and restart the miss is gone. I have poured some seafoam in the gas thinking I have some bad gas. This did not help. My next plan is to drain the tank and install a new filter. The plugs are new. The coils are 1 year old. Any suggestions? Thanks.