I was coming to a stop light from I think 80+ in my sister's cl-s. I was braking hard, but at the end it felt like I was fishtailing. Was that VSA at work? Didnt see the ! light turn on either.

 

The VSA really only comes to play when turning (or losing control of your car). Now if you were really hauling on the brakes and testing the ABS, you get the mega front end dive, and the back end is up, it might dance a little. Were you turning the wheel at all? Or just braking in a straight line?

 

The VSA works through the brakes, engine retards, and throttle cut-off. If you were already on the brakes (BIG TIME), I would make it very difficult for the VSA to try to override the imperative to stop quickly.

Generally speeking, the VSA light WILL come on. I was testing my strut bar on some wet curves at 40-50 MPH, and finally got the light to come on a few times.

I've never seen it come on during braking (but that is only me). Sometimes things can get rather busy -- who knows maybe the light came on (or blinked) and you were very busy...

 

I ve slammed on my brakes pretty hard and the VSA has never gone active on me....only during acceleration or turns has it blinked.

 

Where did you get the "POWERSTOP" rotors?