Graham is right on the money, about the AP Wasp. I've only run one of mine so far, but am impressed with the performance and handling.
The stock R/C carb is terrible, and doesn't come close to the rest of the engine in quality. Conversion to a Cox, or RSM venturi is the way to go.
RSM is marketing a replacement venturi (not Larry Renger's design) that should work as well or better than Graham's Cox conversion.
Problem here, is the price of the conversion, which will probably run about twenty dollars. I happened to have the Cox parts laying around, so have nothing invested but time.
The original AP glow plugs are the same size as the early Norvel plugs, which are smaller in diameter than the Norvel Freedom plugs they used the last few years. The Freedom plugs are hotter than the early Norvel plugs, but I have no idea if the AP plugs are the same heat range as the early or late Norvel plugs.
Considering that the AP Wasp with a conversion venturi, will run circles around most currently available Cox engines you can find for the same price, it's not a bad deal. Add the warranty, and full stock of replacement parts, and your money ahead.
Bill