If any are still reading this thread, Porsche started providing the PET catalogs for free sometime in the past - not sure when, but one day they appeared when I was browsing their website. You can find any PET by going to this page, selecting the model and year you are interested in and open/download it. They used to offer the 959 PET but dropped it a while back.
https://www.porsche.com/usa/accessoriesandservices/classic/genuineparts/originalpartscatalogue/
scroll down a little till you see the drop-downs to select year & model. Still waiting for WSM's, OM's, etc but this is a start.
good luck.