Last week i fitted the modulator kit to my ABS booster.
It is a fairly involved job that is a little fiddly.
It is pretty much an 8 hour job.
I cant say that i noticed any change in the pedal after putting the kit through.
All of the O rings seemed to be in good order bar one, but i dont believe it was leaking.
What was a concern was the spring retainers on the modulator even though the retainers were intact they were very brittle as has been noted these have failed on some P38`s. As mine is the earliest 95 model with 300k on it these parts have given good service.
If you are mechanically inclined this is a straight forward job just a little fiddly.