Late year, when we were coming home from holidays in Florida. My 2000 STS was riding fully loaded, 4 persons, trunk so full that you had to push it shut and a large sports gap riding in the 5th seat. I calculate that the Caddy was weighing in at approx. 6500 lbs. On I75 we came upon a Mustang that wasn't letting anyone pass it. I suspect that it thought that it couldn't be out run. Wrong! The Caddy passed him at around 126 mph. By the time I got off the gas the STS was on its way from 135 to 140 mph and the engine was turning just under 5000 rpm. My STS was still accellerating when I let up on her. It was the wife (in the back seat) saying "do you want to STOP THIS %$#^%$%%$# STUPIDITY" that prevented me from actually finding out just how fast her could go.