When you say "screw" on the throttle link, its not clear which screw you are referring to. If you look at the throttle arm from the side of the engine, inside the arm you will see a small screw. This is the Low Speed Needle. Turning the needle clockwise will lean the low speed mixture, and turning counter-clockwise will richen the low speed mixture. Make very small adjustments (1/8 turn or less) and always recheck the high speed needle after adjusting the low speed. With an 11x5 prop, the Pro 46 should be turning around 13,000 rpm at full throttle, and should idle very reliably around 2750 rpm.

As for glow plugs, I prefer the OS A3 over the OS #8 for my Pro 46.
Brad