The fastest I have been, I'm not entirely sure of. I was driving a company car, 2003 Honda Civic. I was going on north I205 here in Oregon and was on the on-ramp for I84 west into Portland, I'd gotten over into the left lane to pass the slow people and I floored it. I noticed that the cars in front of me were coming up really fast(insanely fast is more accurate), so I took my foot off the gas and started to brake, only then did I look at the speedo and I was slowing down from 135 mph. My best guess is 150 mph or so.
I did manage to get my 1982 volvo 240 to around 95 mph, it's speedo only went to 85, so again another guess.