You didn't mention if your are running manual drums or power disc in the front. I would say remove the master and bench bleed it again. I know its a giant pain in the ass, but worth doing. The master could be defective as well.
When I replaced my master, I put the new one in a vise, then bent some spare lines to dump back into the reservoir. Then It said to push on the rod till you see bubbles. keep pushing and releasing till there are no bubbles. then bend the lines upward, fill it with more fluid, cap it, bolt it on. remove the cap, remove one line at a time and quickly replace it with the new lines.
I would also replace the proportional valve. If you have a 4 wheel drum car, get rid of the distribution valve and get an adjustable proportional valve, or a stock disc/drum proportional valve. Either is better than the POS distribution valve which is prone to failure. I put a repair kit in mine and it was only slightly better, still had an internal leak. I finally replaced all the lines and got a wilwood adjustable proportional valve. My pedal is like stepping on concrete now.