" Nitogen has a larger molecule than some of the elements in air so the gradual air loss is lower."

Not trying to be pedantic but just FYI.

Nitrogen (N) is an element (atom) of an atomic weight of 14 and constitutes 78% of our atmosphere.

Oxygen (O) is an element (atom) of an atomic weight of 16 (therefore larger than N ) and constitutes 21% of our atmosphere.

A molecule is made up of two or more atoms.

A property of N is that it is relatively inert ie. does not readily react (combine) with other atoms to form molecules, unlike O which is relatively reactive and can, theoretically, combine with other atoms in the tire to form compounds that are undesirable. I say theoretically because for all intents and purposes this would be negligible in regards to performance, but in the rarified field of auto racing anything that is perceived as providing an edge will be utilized.