I have a s stik with an os 46 fx, and the other day I notice for the first time that the blow-off from the burnt fuel on my plane was dark in color. It usually is still a little pink, since I burn Omega pink, 15%.......I did run about 85% throttle this time, I usually run around 50 to 60% throttle.........and I have only burnt 3/4 gallon on this new engine. Any ideas would help...