Had my car on an exhaust gas analyser this afternoon and it was misfiring at idle when the mixture was set too lean >1.5 CO or so..might be worth turning the screw in clockwise on the MAF to richen it up and see if it improves.
I would guess that the bleed valve would cause some air to bypass the MAF and lean out the mixture off boost but should think this is neglible.
I have had trouble with non -nissan plug leads causing misfiring so if they are old or non-nissan they might be worth looking at.
On my second cold start idle control valve now and neither has worked properly so i'm just going to live with it now as the car doesn't actually stall and it saves petrol
. I guess a soaking in wd-40 might free it off but never tried this.