That is the standard converter stall test. My turbo does the same thing but you can get an idea of the stall speed.

What counts is to understand that stall speed is the RPM the motor climbs to under those conditions and is typicly above 1200 rpm.

Also try using the E brake as well as the service brake to get a bit more rear braking. I have also upgraded my rear wheel cylinders to get a bit more rear brakes. It give a bit better match to the V6 brakes in the front.

Kevin