If your engine is rattling in flight you have it too lean at that point, so you need to richen the mix. I have mine set to an idle down of 1700, and normal idle of 2000. I get max of 7800 rpm on a 17x13apc and 15%.

Im not familiar with the 8103 but assuming you have a 5, 7 or 9 point curve slaving the fuel valve to the air valve, you need to adjust the point at the stick position where the engine rattles in flight to open the fuel valve more.

I also found the mix side barrel to be stiff when new and had to free it up by lapping with toothpaste, oddly when dry the barrel didnt bind but when fuel was added it stiffened up. The small servos I have used also wear out; and I had a ball link strip the threads. These things caused me some troubles.

You should be able to acheive an idle lower than 3000, if the engine is rich on the idle side it may die after snaps. The high idle RPM makes me think it migh be rich. I have begun taching my engine for high speed and idle, I insure 7700rpm or better and a 2000 rpm idle before flight. It just helps my comfort level.

Glad to see Ivan skirted your shores. I didnt realize Aruba was considered outside the hurricane belt, maybe we should spend our vacations in Aruba.