I have an 86 Van that has a bad ECU.

It runs fine with a borrowed ECU from an 87 with these numbers (Bosh
#0-261-200-284/285) (no VW part numbers on it).

I have an ECU (that I thought is a good working unit) from a 90
Syncro that has the numbers (Bosch 0-261-200-284) (VW #025-906-022D)

But the 86 van won't run with the 90 ECU.

I thought all the 86-91 Digifant motors the ECU's were
interchangeable...

Am I right???.... which would mean my 90 ECU is bad also.....or are there
different versions of ECU's for different the different years 86-90 ??

WC