Originally Posted by blis

Yes, this is due to excessive air, this could be caused by an air leak, so it's always wise to check bearings, carby, carby boots, exhaust manifolds etc for leaks. The FAUX idle is evident when you have cleared the block and crank of excess fuel, specially after a long straight.

Lean the LSN 1/4 turn and see if the idle rises or behaves more consistently, but also consider the engine should be at operating temperature before you attempt a fine tune.

Add to it the fact that your engine uses the methanol to cool and it's best in a state of richness off power and at low idle, this won't harm the rod, crank and bearings as much as a rich top HSN. So in my experience, it's very difficult to get a perfect LOW/IDLE tune and it's safer is it richens and stalls than it is with a LEAN IDLE as it might overheat under racing conditions.

It's really up to you and your observation, every engine tunes differently, operates at different temperatures and many will do it by feel, sound and smell.

PS: Weird or erratic shifting is often caused by a dirty or slipping ONE way bearing.
Clean it with a clean cloth, add one drop of ONE WAY LUBE (it's a thin not so oily lube) or just lube the lay shaft and work in the oil by putting the one way on the shaft to distribute it evenly.