So I filled my tires with Nitrogen too.
See this thread:
Got Tires filled with Nitrogen.
Pretty cool really. I happened to be at a meeting at the factory that makes the units which filter Nitrogen out of the air to fill tires. The unit deflates the tire to 2 PSI, refills then deflates back to half PSI and reinflates a final time. This guarantees something around 95-98% Nitrogen in your tires.
See the link in that thread from Carbeaux