Just installed Motordyne 3/8 spacer and Z-tube and I noticed a light layer of oil inside the plenum and a small dark oil ring around the circumferance of the throttle flap thats inside the end of the plenum where it connects to the Z-tube. Is this normal for a G with 51k miles or could the oil have come from a JWT pop charger I ran for about 8 weeks a year ago? The JWT pc was oiled from the factory and when the color faded I removed and cleaned it and was not sure how much oil to sray on so I went back to stock. I also did not like waiting a day for the filter to dry.

 

the oil you see is from the PCV (Positive Crankcase Ventilation)...
The blow by and oil fumes in the crankcase are sucked into the intake per smog requirements. They are then 'burned off in the engine'...

It is not a perfect solution, but they have been doing it for 30 or 40 years now.
If it really bothers you, Stillen (and maybe others) now offer a 'catch can' system to trap most of the oil so you can just empty once in a while.

But no worries, it is totaly normal.

 

If you go to your local Infiniti dealership, they offer a "cleaning service" where they clean out your intake, from your throttle body through the manifolds. It's pricey but it should clean all the junk out of your system. I'll probably get this service at/around the 30,000 mile mark (unless it's called for sooner).