While it is unusual for me to hear that it cuts you off at only 90 MPH (Usually Contours cut out at an indicated 110-114), it is not unusual to have an electronic top speed limiter on any vehicle. Get a chip from Superchips, Diablo chip, etc. and that will allow you to travel as fast as your engine will let you go.
Of course, do not ever travel this fast on a public highway...
