take the fitting/line off of the rear master cyl bowl half for the discs & stick a drill bit into the brass cone in the MC port & you will feel the RPV if it has one (its just a piece of neoprene and a spring) & if so pull the cone & toss it. confirm that you have ~.020" clearance between the round pushrod nub end & the bottom of the piston recess which I'm thinking you adressed when you seperated/pulled the MC forward. All that is left is a prop valve or line blockage. EDIT or a booster or linkage problem under the dash issue.