Well, Luigi must have made you a special carb for your ST2300, because the rest of us got some real losers. I have 2 of these engines and have seen 2 other examples in friends' planes. They all display the same problem - mixture is too rich at about 1/3rd throttle. It cannot be adjusted with the mixture screws to cure the problem. Now, if you don't fly at 1/3rd throttle you will never observe the problem. The engine runs fine at idle and at full throttle with instant acceleration, just don't try to fly at 1/3rd throttle for very long or the engine will load up with fuel and die.

Easy fix is Conley/Perry Mega carb #5001. Or you can go after the stock carb with a dremel tool on the barrel slot to straighten out the "dogleg".

I like a 17x8 APC prop and 25% nitro for My ST2300 for my Sig Cap - big power and dead reliable with the Conley carb. Also be sure and use a good hot plug. Everyone I know uses an OS-F plug with great success.

The only remaining problem is the factory's inability to produce engines or parts until they complete the move to China. Don't crash it or wear out anything!