your idle is playing up because there is a leak in your vacum line that goes to the top of your bovs.
If the bovs were stuffed and the piston inside didn't seal you would have the equivilant of a leak. If they are new its not the bovs, more likely one of the vacum hose's (as there are two one from each turbo and for each bov) has a small hole in it, or is not connected properly.
The oil issue is an problem (mostly likely) with the guage, all the nissan electrical ones play up at some point, mine is playing up atm as well. Get a cheep mechanical one installed under the bonnet so you can see if you have pressure when the other fails.
The oil "light" is separate form the guage and if it is on.... you have no oil pressue (pump) or no oil, STOP your car, check oil and walk. It is very rare to have the light fail by comming on. and its bad if its on. :headspin:
come on, In what way does the water system (radiator etc) effect the oil pressure? thats just silly.
and you do realise that the "engine" oil light/guage is not connected to the power steering oil? as its a completly seperate system and is completly different oil, not even the same colour.
but keep checking it, and you might want to watch the steering oil level as your wheel might :flamed: stop spinning