I run my little bike repair shop and a customer came to me with a bicycle with Shimano's Dual Control setup: http://www.cambriabike.com/StM966-BRM965-PreBled-Hydrlc-Disc-Brake-Kit-XTR-Grey-Fr-750mm.asp
Braking was extremely poor, and although we couldn't see oil escaping, I was eventually able to confirm that both calipers are letting oil go around the pistons.
The levers themselves show no problems.
He would like to replace only the calipers, if possible, because he likes the Dual-Control levers.
I'm thinking about two possible issues: - Connecting the line: is that the same connection since that time? - Oil flow: Does, like with the short and long cable pull "standards", the amount of oil pushed from the lever and the pushed surface in the caliper have different combination or does it simply not matter from a fluid's mechanic perspective?