You might want to try posting your question on the Vintage forum. I don't know why that forum isn't listed in the technical section since 99.99% of the posts there are technical!! Anyway check out the links at this site
http://www.bmwcsregistry.org/Technical/D-jet.html
and the Djet section on this site:
http://members.rennlist.com/pbanders/
for lots of good Djet info. Sounds to me like your MPS is not adjusted properly.