To add a bit, there is no reason in Race07, and many other sims also, to use a chutch when shifting gears. There is no reason to blip the throttle to match rpm's.In Race 07 you do not need a clutch to start a race with, just raise the rev's and punch first gear. Of course, you may use the clutch in a realistic fashion if you so desire. Some have said you get a faster shift using the clutch, but I doubt it.
With autoclutch turned off, you need to depress the clutch or get the transmission into neutral before the engine quits when you spin and a restart of the engine can only be done if the clutch is depressed or you are in neutral.
The same holds true if you have gone to the pit to take on fuel.