Made a Turbo head for it. It wasn't making more than a couple hundred rpm more. Couldn't measure it anyway. Looked at the stock plug, and there was a .030" step down to the plug on the inside. Removed the .030" and got another 400 rpm on top of what I had. Up to 20,400. An OS plug would need a further .030" removed to be correct. 15% fuel gave me another 400 rpm. up to 20,800. Fairly comparable to the Fora. (the Fora is meant for a smaller prop though) and 1/3 of the price. I hogged out the muffler, but haven't ran it yet. I should have got a baseline with it stock. Kind of disappointed that the Turbo head didn't give me any gain, It took a while to make, and the other motors really woke up with it.