It's hard to imagine that a car is street-legal these days without a speed limiter in the US. But it's still possible that it doesn't have one.
Even the V6 camaro had a speed limiter!
(Like at 112MPH or something)
GM limits the cars to what the stock tires are supposed to be rated to. The Trans Ams were limited electronically to 153 on Z rated tires (OEM).
These tires that come on the sport package are R rated. I'd like to see if the Z comes with a limiter because of that fact.