Quoting myself to update this post too. I installed
ECS's bronze caliper bushings the other day and it finally gave me the firm pedal that I'd been chasing. Pro tip: rebuild your own calipers instead of buying some shit rebuilds from Centric (or anyone else). They use the cheapest, softest excuses for rubber guides that I've ever seen and it had me thinking there was air in my lines and needlessly flushing expensive fluid through them for the past year.