sent a friend request thing...
The blurb in the 'borrow car area' says you can use the car - but you can't buy bits for it or go to the GTAuto bit.
All three of my C60's are pretty much bog standard... two of them have been detuned for 650pp races... But I guess it is easy to swap the tune to a normal one in the settings area. All three can win the 650pp seasonal events.
Set ups are a personal thing anyhow... Remember that two are detuned. (Restictor plate/ maybe ballast) -
If you find a set up you like, write it down as I think when you swap out of a borrowed car - it (the car) forgets any set up changes you put on the car.
Have fun... and try not to blow this one 007