I have looked at 2 stroke engines and understand them well but I can't reconcile the two fuel line inputs and the open mainfold hole in the back of the engine. how is this setup and work?

The "fuel nipple" on the engine, typically between the crankshaft bearings, is a vent/drain hole. it just allows blowby gasses and oil to exit the engine. The blowby gasses and the oil that gets by the piston is where the internal lubrication comes from. You just connect that to a piece of tube if you want to route the dripping outside of a cowl and let it drip.

The muffler pressure line and carb fuel supply line are basicly the same as on a 2-stroke, unless it is a pump equipped engine. If it has a pump... then the manual wll tell you how to deal with it.

MAgnum RFS ships with a nipple on the intake manifold, which is intended to be used as a "PCV" cnnection, but they don't always put the tube on for you...

Run fuel line from the PCV connection on the manifold to the crank breather near the engine's crankshaft bearings.

I SHOULD have thought of this... Not all 4-strokes have it, and somehow I managed to forget about it.[&:]