F1 cars do not benefit much from slip streaming and in most cases it slows them down as they loose downforce which means less grip and braking force... For slip streaming to be effecive they need to be almost touching..
I,m no F1 Guru I just remember watching a program about it on the Tv was quite interseting and showed how Aerodynamic an F1 car is. F1 cars leave wakes behind them like a boat and a plane, this is what is refered to as Dirty Air.
I agree that slipstreaming doesn't work in corners because of the dirty air effecting grip but on straights such as Monza and Spa slip streaming gives you a good run on the guy infront because he is punching a hole in the air. Get within half a second and you effectively have a big Fduct.
Slipstreaming in this sense is used all the time in F1 and even touring cars so should be in the game. I can get a really good exit and be 10mph quicker down a straight but sitting behind another car doesn't give me anything extra when it should and they just pull away.
http://www.youtube.com/watch?v=8sxg39qPaA8