Fastest I have been is a tad over 140 MPH in my Camaro, but I had the roof down so it seemed like I was going a lot faster because of the noise. The car just kicked into 4th gear at around 130 MPH so I think I would have easily hit 160+ if I still had enough road (and enough balls)
If I had a small child in the back seat they probably would have been sucked right out of the car.
I can't imagine going 100 MPH faster than that. I also discovered that my stock brakes aren't really the best when trying to stop while doing that speed.