I don't remember what the exact number was (maybe 75mph) but I had a rental for a business trip out west somewhere--maybe Arizona--and it turned out the car had a governor set to whatever the number was--which at the time was presumably significantly over a lot of speed limits but was right at the speed limit where I was driving. It was very annoying as the car would suddenly drop the throttle and slow down. Only time I've ever seen that though there may be governors set to speeds I just don't hit in other cases.
There is a gentleman's agreement between many manufacturers of street legal cars to produce vehicles that will not accelerate to faster than 120-130mph unless some special conditions or limits are met.
