with a helper you might crack a bleeder to see if it is a psi prob or a piston/square seal (mechanical) caliper problem. If its psi then tighten the bleeder back up & being carefull not to intro air into the system & crack a line right at the MC next to the firewall (for the front discs) & see if that relaxes it which if so points to an internal MC prob as opposed to something downstream. Holler how it turns out. k.i.s.s. I'm thinking just bad calipers not retracting enough