yama450yfx,
I can't blame you for trying to be extra cautious about the air cleaner system. I am not sure that your really gain anything by oiling the plastic air box. With an accumulation of dirt on the inside of the air box, you stand a chance of dislodging it when taking the air cleaner out and there-by getting some dirt down into the intake. I can't speak to anything but the standard foam air cleaner. Starting with a clean air cleaner then re-cleaning it as often as needed will make the job much easier in the long-run. I always us a little Simple Green on the inside of the box but never saturate it. I have recommended in past threads, having a new un-oiled cleaner on hand and just removing the dirty one, placing it aside, clean the inside support, wipe out the box and then oil the replacement (preferable with a water soluable oil so clean up is much easier). You can clean the dirty filter later on.
Just my way of doing this easy but critical job.
Sid