[pormgb]

I got this figured out!!

My problem is related to rear caliper piston position, GM Metric calipers have this weird adjustment that is related to the parking brake.

For the calipers to function correctly, the pistons have to be adjusted so the pads are close but no obstructing wheel moment. The parking brake also has to be attached.

The rear pistons are sitting so far back there is excessive pedal travel taking up the slack, I moved the pistons up using the parking brake levers and the brakes are now functioning correctly.