Adjustable Prop. Valve is a must , otherwise your brake bias will be off. Keep in mind, you must remove the factory proportioning valve as you cannot have 2 prop. valves in place at the same time. Some minor brake line work and adapters required for the rear line where it comes out of the old factory proportioning valve. I also installed 2# residual pressure valve in the front brake line and 10# in the rear line (as close to the MC as possible). Am very pleased with the brake performance now!