While pulling the stock inlet tube off after about 400 miles (for installation of the AVO Inlet Tube), saw this buildup already in the throttle body.
It's that black line running along there.
It was easy enough to remove, I just put some brake cleaner on a rag and wiped it off with a bit of elbow grease.
It does make me wonder how effective the standard Toyota air filter is, given that it has only been 400 miles, and it's not exactly pollution heavy here in Seattle. Checked the inside of the inlet filter, and it's not from blow by oil.