I am looking for any ideas as I am all out, so any help is welcome.
I have a 96 D1 that I have replace the master cylinder, and abs pressure reducing valve. I now have brakes when I pump them several times. However while driving or if left untouched for even a short period of time they seem to bleed off,(no brakes). I have bleed the system several times, no air. could this be a bad booster? Or another problem I should investigate??

Did you bleed the brakes with nanocom or similar??

Sounds like you still have air trapped in the abs unit!