I have replaced all brake Flex hoses, front.

I have replaced all brake flex hoses, front rotors and pads, rear spring kit, and rear shoes
the car still going straight when brakes are applied the car the back of the car pulls hard one direction and the front brakes harder on the opposite side so the car looks like this under braking (\)
Everything makes me believe that this is the proportioning valve because of the uneven where of all new pads and shoes. Did I mention the calipers are new also. Where is the proportioning valve on the olds cutlass ciera. Is there anything else that could cause this to happen?