I have a ’95 Villager with 320,000 Km and after driving about 100K with the check engine light on (in spite of replacing the O2 sensors), a friend replaced the Back Pressure Transducer (BPT) hose -- a $9.95 item -- and the check engine light has never came on again.
When he took off the hose, the hose just about turned to powder when he squeezed it in his hands during the removal.
If you got an EGR Code 32 or DTC P0400 this could be the problem. I think there is a service bulletin TSB 98-052 addressing the BPT hose.
Hope this helps.
Pylet