This is a cost effective upgrade for anyone with an EF:

When I was upgrading my brakes and brake lines, a friend of mine suggested I find a master cylinder out of an '89 Integra. He said he saw on Hybrid Honda how it bolts on and works better. I went on there after, and of course couldn't find anything.

I went out on a limb and pick one up. Sure enough, it bolted on and worked better! The diameter is still the same as an EF, but apparently the valving inside is slightly more "aggressive" (for lack of a better term?)

Only thing that had to be changed was the forward most line had to be bent down so that the fitting would thread into the cylinder's outlet.