This game has things completely backwards right now, no option to disable tuning in lobbies, and no tuning in Sport mode races.
I think they should have both in Sport. Having it rotate as well.
N### = One Make No Tuning
Gr 4 = Any Make Any Tuning
Gr 3 = Any Make No Tuning
N### = Any Make No Tuning
Gr 3 = Any Make Any Tuning
Gr 1 = Any Make No Tuning
As for the main reason for the post - GTS really needs "No tuning" option for player made lobbies. .. and "Shuffle Racing"