The plug in the center on the side is manifold vacuum all the rest are for coolant.Most people use the two on the side for hose fittings to flow hot coolant through it, the two underneath are a little close to the exhaust,and the center underneath is best for draining. Heating can help when you have sloppy fuel delivery (puddling,large droplets,too much carb,to big manifold ect) but nicely atomized fuel in a colder manifold will give you more power (VE).Im also in CA and do not heat my manifold. I think if you try the offy you will like it. Good luck
