Hobbsy told you about the idle bar plug. Adjust the high end first. When you adjust the low end, be careful not to move the throttle arm or you will have to reset the idle. Use the pinch test and the "hold the plane vertical at full throttle" test.

if it cuts out in flight, it may be too lean. This engine can run fine in a stand but need to be richened up for proper in-flight mix.

Good luck. Those are good engines, IMHO. Careful with it though; Horizon is out of crankshafts(!).

Regards.