Shawnsheridan is the man!
He figured out that for the F15 M performance brakes the correct code is
SBRE and I was able to follow the steps to code my car to have this functionality. My brake pedal is no longer sinking lower and it feels like it's back to stock position but with much better braking!
At first right after saving the code to the car I didn't notice any change in the pedal but once I started driving it the pedal firmed right up to what I would expect a big brake kit should feel like.
Very happy now
Alan