I have 25hp kolher with 1,600 hrs. When it is started cold it throttles from low to high speed quickly. After I run it a while and then put it on the traler, it will be sluggish to go from low throttle to high throttle. You can see black smoke if you slam it to high throttle. If you ease it back down then run it back up slowly, it will usually go back to high speed. The Kohler rep suggested testing firing using an inductive timing light and I plan to do that when I either buy one or borrow one. He thinks the SAM might heat up when the engine is turned off since the fan stops. After the engine runs a minute or so, it might cool down and then start working correctly. Anyone agree or have other ideas of what to check. Both coils are good and spark plugs are net. ENgine runs great when it is at full throttle.