Brake Bias Valve. What do i need?

[antnicuk]

Since fitting bigger discs on the front of the FC they lock up a lot easier and i dont feel i am getting the full benefit.

I tried fitting a pad with a little better bite on the rear but the fronts still lock up way easier than the rears.

I am gonna rip out the ABS as it doesnt work so i will run new pipes and thought it was good time to do bias valve,  

do i have to remove mazda\'s one some how or is that done via the master cylinder

any help or advice greatly appreciated.