use a propane torch, not lit of course, and gas around the intakes and carbs to check for air leaks. what is the exhaust doing? one side different or smoking more/less?
Could be evaporated premix dripping off of the stud too, from a carb leak. - For your rev problem... Pull your air cleaner and look if both slides are bottomed out.
Coolant leak is your o-ring on the coolant tube going into the clutch cover. It will allow coolant to leak onto the top of the engine and run through the drain hole and off of one of the lower studs. It will not leak into the trans as long as the side cover gasket is good. Have you had the clutch cover off recently?