I'm struggling with the same low pedal situation on my lexus.
I've changed pretty much every part i.e brake booster, master cylinder, pressure check valve, rotors and pads. the only thing i can think of at this point is whether the new master cylinder is bad as well.
I have asked this question in the forum but no one replied. What's a good way to check if the master cylinder is bad ? a manual diy check i.e... ?
Whether you think you can or cannot, Either way you're right!. by Henry Ford.