Is the pushrod in the brake booster adjustable for the MS6? If so, make sure it's adjusted properly or you could end up with either excess play in the pedal or unintended lock-up. This process was a royal PITA on my RX7 because, even though the FSM specifies the procedure, it requires special tools from Mazda, which no one has. Basically, I had apply a vacuum of ~20 in. Hg to the booster and check the clearance between the pushrod and the MC. Because I didn't have the tools I ended up shortening the pushrod to its minimum, put some red bearing grease on the end, and increased its length incrementally until I saw contact with the MC, then backed it off 1/8 turn.