Your exercise reminds me of my VFR, i had it about twelve years, i never found the air filter
The only mod i did was a cheap small end can from Ebay,,i sure used that bike,,thrashed it trying to keep up with the Gixxer thou of my mate.
Such a good bike that was,,i hope these Yams are as good,.
As for lean burn, it will depend how rich it was running before you changed the filter.
Take a plug out and photo it , then recheck after a thousand or so miles,see if they turn white,black grey or burn