What Master Cylinder for 4 wheel disk brakes?

I have a power booster. Works a hell of a lot better that the one I took off.

The original post was asking about manual, - there's a world of difference, so I wanted to be clear about which sizes of master cylinders you were comparing, and if in fact you were not using power as asked.
You might try a 15/16 from drdiff, see what difference you find in performance feel, - you may toss the power, as many do.
Good luck.