Oil on MAF sensors

I have a 2007 F430, a couple of months ago it threw a check engine light, lean faults in both banks. I ended up finding both maf sensors were coated in oil from the crankcase ventilation system. I checked the oil level (engine hot and running), oil level was ok. I removed the intake boots and cleaned off the mass air flow sensors. I put roughly 600 miles on the car without a problem, last week the check engine light came back on and the bank 2 mass air flow sensor coated in oil again. Does anybody know if there's a pcv valve somewhere that could be sticking? Maybe part of the valve cover?

 

I checked the oil level with the engine at operating temperature and running, it was halfway between the marks on the dipstick.

I'm almost positive its an issue with crankcase ventilation, the air filter is stock. I've thought about reducing the diameter of the pipes but I'm just worried about crankcase pressure getting too high and blowing out gaskets.

 

Thanks, I'll try running it at the minimum mark and see what happens.