Yesterday in the way back from a car meet I pulled on some ***** in a BMW and once I touched 115, 120 mph it all of a sudden got MUCH louder and sputtered a little, almost like a rev limit but not even and it definitely didn't feel like it was supposed to do it. Car is a 2000 Z28 convertible with an A4. After getting off the freeway it drove fine at normal speeds. Any ideas? 😥

 

You don't say at what rpm the problem occurred, but if it was at high rpm it could be valve float.

 

speed limiter? If the car did not come with the oem z rated tires, then the limiter was set around 120 due to the all season tire's lower rating. Being a convertible maybe had a lower speed limiter too?