I have a TT. 46 and when I ran a 10x6 prop it would shut off quickly. I swapped to an 11x5 so it would come in slower on landing but now when I kill the engine it takes about 7-10 seconds before it dies. The carb is as far closed as it will go but it just doesn't want to shut down quickly. What could cause this? Unbalanced prop or air leak somewhere? Other than that the engine is flawless. Thanks.