I just put a Stillen Intake in my truck and now have my drop in K&N filter (33-2286) for sale; it is a year old and has ~1,400 miles. I also have a new NISMO oil cap that I'm selling. Not wanting to pay >$70 for the Genuine NISMO oil cap, I opted to try the less expensive version and accidentally ordered two when I first bought my truck Feb of 08. The quality is great (machined aluminum) and the one on my truck still looks as good as new after ~2 years.
The filter at AutoAnything is $45.14:
2008 Nissan Frontier K&N Air Filters, K And N Filters
The Oil cap is $25.00 after shipping on Ebay (I got it from Amazon, but it's not listed any longer):
Nissan Nismo S13,S14,S15,GTR Alloy Oil Filler Cap:eBay Motors (item 180302603500 end time Jan-21-10 09:42:30 PST)
I'll sell both of them for $50.00 shipped in the 48: via paypal. My zip is 29492 in Charleston, SC. Everything shown in the pictures below but the carpet will ship out.
EDIT: the cap label has a protective plastic film on it that's why it looks like it does. And it sticks on after the cap is screwed on so that it will line up with the front of the truck.