Can timing way too far advanced cause blowby? ie; oil on dipstick tube, oil coming out of crankcase breather tube(into plenum), oil around oil fill cap.

Timing shouldn't cause any of that.

No. Not until the detonation from the over-advanced timing kills the rings or knocks a hole in the piston. Then you'll have plenty of blowby.

How's your crankcase ventilation system? In good, working order?

The pcv valve is new and all the lines for the crankcase ventilation system. When the engine is running I dont hear any pinging or knocking, but I know the timing is off. The car bogs and acts sluggish when first taking off, then when the rpms get around 1800 it seems to run better but still seems lacking in power. It will stall when cruising at low speeds, like through a parking lot, but it does not stall when stopping for traffic lights. It is a 1990 350 with about 120,000 miles, ran perfect and never burned any oil or had any signs of blowby. After installing a Crane Powermax cam, headers,roller tip rockers and double roller timing chain, I have been chasing one gremlin after another. I just cant understand why it was fine before and now it has this blowby issue. I will do a compression check and see what that tells me.