Does anyone know if there are any upgrades to the standard, a larger size and which cars they would come off?

Have you installed new calipers with a bigger fluid capacity, resulting in longer pedal travel?

That's the only reason I can see for wanting a bigger master cylinder. With the standard calipers you'll give yourself more brake jump in, making it harder to some on and off the brakes smoothly.

No its something i done with my M3 fitted a group A master cylinder that was a bigger diameter and it improved the brakes no end, just wondered if it was a common mod for VAG cars?

Also ive got porsche 996 brakes on the front of my car and to be honest the master is fine for them, just wanted a bit more ummpfhhhh

Obviously there is nothing!

Not sure if there any different OEM ones which would fit. All the VAG ones are the same diameter AFAIK.

The MC is made by ATE though, so they may have something from a different make car which may fit.