I couldn't find the schematic, but googling I did find this and remember you said the oil pressure was 4.5 to 6.5PSI. 4.5 should be the limit according to the bentley manual (regulated pressure).
Reading the first part of the picture :
This says that when max pressure is applied in default mode, the vanos goes full retard.
Did you do the test cold or warm?
Did you get pressure at idle?
if you did get 6.5PSI cold its suprising, warm its alarming. Too much pressure is just as bad as too little pressure and that would point to the pressure relief valve not relieving pressure (stuck closed).