tiktock

went flying this evening and no difference. the engine wants to quit on down line. i tried a knife edge and the engine was fine but after a few seconds in a down line and the throttle at idle the engine just starts to sound real funny and i have to level out for the engine to stay going. other then fuel pluming/installation, would a wrong needle setting cause this? also i've noticed when i touch the tip of the muffler i get this black oil on my fingers, is that normal?

thanks