One other thing that you may want to do. If you didn' have this problem, before you replaced the proportioning valve, you may want to bench beed the master cylinder. If the master cylinder internal chambers, not the reservoirs, had air introduced. The only way to get it (air) out is to bench bleed the master cylinder. This can be done one the vehicle if you have the bench bleeder hose kit that comes with a master cylinder when you buy one. It's called "bench bleeding" because you typically do it before you install it when new. It can be done buy disconnecting the brake lines at the master cylinder and connecting the hose kit to the master cylinder. the other ends of the hose kit goes into the reservoir. Keeping the fluid level full, very gently depress the brake pedal until there is no more air coming out of the hoses into the reservoir. Press the brake pedal quickly and you will have a brake fluid mess all over the place. Paint does not like brake fluid, unless you want to remove it. Best of luck in finding the trouble and remember this is fun.
