look where the OBD2 interface is. See if there is a control harness connected to it. Or if there are TWO of them.
I work with a company that puts these limiters in their Ford E Series Superduty trucks. It limits the speed to 55mph max. If you disconnect this device from the OBD2 connector then the speed limiter is ineffective. You may have the same thing. If not then a trip to the dealer to reprogram the top speed in your PCM is needed.
"My 98 Oldsmobile is so Super Sperrrrrrrrm! Suckers to the side I know you hate...my 98!! You gonna get yours! Get with it, the ultimate homeboy car."
Public Enemy "You Gonna Get Yours"