Thanks for the information.those are not the gm-specific mongoose cables (in fact they are listed specifically as VAG) and will likely not work.
that's the proper cable at least (gm2) but i'd be concerned about authenticity... there are clones floating around out there.
i was not able to get tech2 access on my '99 93. it seems the mongoose is really for CANBUS cars. however, i did not spend a lot of time troubleshooting as i lent the car to a friend.
I got to get the TECH 2 knock off and just experiment with the 99 93 and see if it would work also with 91 GMC.