I reckon you are running 4 spots on the front (or VT/VX commo calipers), and you are using the 50% max bias valve. There are two sorts I believe.

Measure the cross sectional areas of the front pistons in your current calipers, and compare them to a R31 skyline..

I run VR caliperso n the front and commodore VR calipers on the rear. I use a 180B master, and bias using a wilwood valve on the rear line.

Maybe you are still running the 'splitter' valve?

This is what I'm thinking.

PS. I'm not real sure that the rear residual pressure valve in the master cylinder needs to be removed actually.