GM Service Manual Online
For 1990-2009 cars only

All engines have electronic engine speed limiting to 2,550 rpm.

Engine Road Speed Governor

This system controls maximum vehicle speed automatically and reduces engine power until vehicle speed gets down to maximum governed speed.

A 75 mph (120 km/h) road speed governor is standard for most models, but can be programmed to any speed below that default setting. Other models have a default setting of 80 to 85 mph (128 to 136 km/h). You may have a label on the headliner of your vehicle with more information on your engine road speed governor. See your dealer for assistance with programming your engine limited speed.