That's crazy PIGDOG. mate, im sure you have tryied these things but im only trying to help.
Make sure you dont have a leak in a line and that the air has been all pushed out.
Also check the push rod inbetween the master/booster hasn't fallen out.
Try Clamping up the break hoses and pump the petal to see if that fixes the soft petal and pin point the problem for you.

let us know how it goes.