I don't even know how it works. How can you change pressure from left to right in the front?
All it is doing is softening the pedal and killing total pressure to the front.
Take the thing out of the system and throw it over the fence at the Chevy guy. It is garbage.
It is not a resale feature on a car.
The stock rear brakes are so weak, no proportioning valve will help balance anything unless you put bigger brakes in the rear.
The rear caliper is a go cart caliper. That's where the thing belongs.