ok...I've been reading this thread from time to time since hwy 9 is mentioned. Whatever you guys/gals do, please don't be dumb out there. Hwy 9 is very popular for motorcyclists and there have been many instances where a car has gone over the DY. Yes, many bikes go over the DY too, I know.
A buddy and myself almost got killed by a red pontiac sunfire on Del Puerto on an early morning ride a while back. The driver was half in our lane and nearly struck my buddy ahead of me. By the time the driver reached me he was still 1 ft over the DY with tires screeching.
A while back some peeps from a RSX club went for a drive on Stage Rd (I think). One RSXer went over the DY on a blind turn to make a pass. A group of motorcyclists were coming from the other side and one rider was struck. He made it out ok, but got hurt pretty bad.
If you're so set on pushing your car on the street, be safe. If you really want to push it, keep it on the track. If you want an additional challenge, try out hwy 9 on a motorcycle if you haven't already done so.
edit: something useful from this post
Go at 60-75%, leave the other 25-40% to unexpected stuff like deer, gravel, and other vehicles.