I have a supertigre 90 engine that I also had trouble with when new. I bought it about a year age and have it in a Patriot XL. I have run about two gallons of fuel through it and now it runs great. I had the usual mid range rich problems, and the idlewas not always dependable. I run a 12-8 or a 13-6 prop on it. It idles about 2000 to 2200 RPM. The top RPM with these props is right around 13000. As far as your idle problems, I think I would try the "pinch test". This will tell you if you are rich or lean on the idle. I suspect you may bealittle too lean on your idle setting. ( I just went and checked my idle setting and I am running exactly 2 turns out from fully closed ) I would start with an idle setting of 2 1/2 turns out and see what happens. Of course you set your high speed first and then work on the idle speed. These engines are not the same quality as an OS, but they are about half the cost. They take a lot of break-in time and a lot of fiddling to get them right, but once you get them right, the just might become one of your favorite engines. I know my ST -90 is. Let me know if you need more help.