After 150,000 miles on average these 1uz-fe motors tend to use a bit of oil from my past experiences.... I use to own a used dealership and had the SC's, LS's that I bought and sold. The ones with higher mileage always seem to use some oil regardless whether they were dealer maintained or not...
Don't know why they burn? Must be piston ring damage or cylinder wall imperfections over time... Even though some used oil they all ran like new...Kinda like my current SC400 that I own now...It uses about a quart of oil in between oil changes but I absolutely beat on my ride almost daily..
My currently owned and modified SC400 has 110,000 miles on it and has been maintained to perfection but still uses some oil...My Nitrous application probably has alot to do with it would be my guess...