FD Oil Metering?
 

I am a bit confused. I'm tring to figure out how the oil metering works on a FD RX7. I realise that the oil metering pump contains a stepper motor which is ECU controlled. My question lies in how the oil actually enters the engine via the two one-way nozzles. Each nozzle has a vacuum hose plugged into the top of it.
In the earlier 86-88 Turbo RX7's this hose is fed by air after the intercooler (after running through passages in the throttle body). Therefore it sees boost pressure but not vacuum. This seems to make sense to me as the pressure in the hose will always be at least as high as the pressure inside the motor. Therefore, the one-way valve should be open and the oil (supplied via another line to the nozzle) should flow into the housing (possibly mixed with some air).
However, with the FD these hoses simply go to filtered air (between the air filter and turbos). This means that the hoses will have approximately atmospheric pressure applied to them or maybe a little bit of vacuum depending on how good your filter setup is. So whenever you're under boost making more than atmospheric pressure, no oil would flow into the engine. But wouldn't this be the time when a bit of extra lubrication would be needed most? I'm sure the Mazda engineers had a clever reason for the change, so the odds are that I'm looking at the system in the wrong way. Anyway, I can't get my head around it. If anyone has any info/theories I'd greatly appreciate it.

garfinkle tells me that the vacuum lines are there to draw vacuum on the oil when you turn the car off to keep oil from draining into the motor from the small feed lines.