I bought the MaxiDas specifically for a 91 GM with an early OBD1 system.  You can imagine my disappointment when I discovered that the Maxidas only covers 96 and later even though the OBD 1 link connector is included.  Tool has tremendous potential, but until your clever engineers figure out a way to support 91 gm obd1 systems, the tool is not meeting my needs as a customer.   Furthermore, it seems that it was falsely advertised.  The product brochure indicates that the Maxidas platform provides "deep vehicle system coverage for all makes and models."  I hope your development team has plans to expand the vehicle coverage to include early GM OBD1.