On VW/Audi cars, the Master Bracket dramatically reduces master cylinder/firewall deflection and improves brake pedal response as a result. Instead of flexing the unibody sheetmetal, all brake force is immediately transferred into squeezing the calipers.
Here is a trick picked up from the venerable, Porsche 911. One of its many quietly celebrated virtues is incredible brake pedal feel. That's largely to do with how solidly the master cylinder is mounted. The design theme is replicated here.
Installation in a VW Mk5/6, Passat, or CC is relatively simple and should take about 25 mins with simple hand tools. Due to sheet metal differences, the Audi TT cannot be fit with this part.
Master Bracket Install