In GP2 there is a problem, you see the other cars with F1 shapes when your in the cockpit and also when you use one of the many camera views. But there is a solution for it.
You need to have GP2lap installed for this !
With Gp2lap you can change : SvgaRcr1,SvgaRcr2,SvgaRcr3
Higher distance increases the PO (processor occupation)
You must try out which settings are good for your PC (10000, 20000, .......)