[konwal455gto]

I have a 65 GTO it had power brakes with stock single master cylinder. The brakes were always touchy , I thought, it was real easy to lock them up. I and my crack mechanic both looked at everything could find no reason why. Moving ahead master cylinder started to leak, brakes became less touchy. Decided to replace with a dual master conversion. New booster and master cylinder for a 68 corvette with drums, was told it was a good for a conversion with stock drums. Now brakes are really , really touchy . WHERE DID I GO WRONG? Thanks Bill