Ususally there's a good mix of cars during a Friday test day. Usually it depends on what event will follow on the weekend, say before a VARA race there'll be lots of older ITB type cars out there along with a mix of production cars. I'd still call the track to make sure it's not going to be a motorcycle T&T day because the next event will be two wheeler's (Aug 11-13). You're best bet is to drive the line and be predictable, let the faster car make the move to get around you, and they will. This works for when I'm being passed by GT-1 cars and when I'm passing H-Production cars. If you feel like you're being crowded, take a detour throught the hot pits and let them by. You should get plenty of open track time. I'll be out there on the 31st.
James