ZVex Wooly Mammoth clone problem

[CCS]

Hey All I've built (attempted to) a Wooly Mammoth Fuzz clone from wiring diagram I downloaded. See attached. Output signal and Fuzz are both very weak to the point of reducing volume of amp. Has anybody built this pedal and experienced the same problem?
If so could you please shed a bit of light on the possible cause and suggest a fix. Thanks Paul