Are you sure the tune is applied and its already in that class. If you have a car and have say an a class tune applied the car will not appear at all even if you could put a b class tune on it. IIRC when i was running abc's quite a while ago basically your best bet for cars that worked in multiple classes, is to own 3 different cars and have the tune for each class applied to each of them. Like say an s2000 i think can be used in c, b, and a to some success. own 3 put a c tune on 1 a b tune on one and an a tune on one. That way you dont have to try and load the tune, because if you are in the lower class they dont appear.