so, my mpfi has 3 crank vent spiggots. one on each rocker cover, and one near the rear of the engine, on the block. can i plug the one in the crank, and just run the valve cover ones like normal, or is it better to have it breath out the crank too?

Uhm, the original intention is that you draw blowby gases directly from the crankcase spigot, with throttle body vacuum.

The valve cover spigots are there to allow fresh, filtered air into the engine.

Take note, this is opposite to most other car makers, who choose to draw from the valve cover and let fresh air into the crankcase.

Subaru system is better, because it removes potentially harmful blowby gases directly from the crankcase, instead of pulling them through the entire engine!

 

If you have modded the car extensively and lost the original "Positive Crankcase Ventilation" spigots on the intake, I would suggest a couple of those tiny K&N breather filters, one on each valve cover spigot. And then find some way to connect intake vacuum to the crankcase spigot. You must use a PCV valve in the hose, to avoid sucking too hard and prevent backfires from igniting gases in the crankcase!!!

 

Don't disable the PCV system, your engine oil will be under attack from the blowby.

i have filters on the valve covers now, and the case vent is plugged. could i just put the crank vent right into the pcv on the manifold?