I'm pretty sure the 92+ motors are compatable.. but don't quote me on that. Also, I believe there was a member, or information on this topic somewhere around here. The 92+ are also much faster, IIRC. I know the problem with mine, is they aren't getting enough current. Test it out, if you want. Sit in the Driver'* seat, and raise the window, after it has started to move, have a friend get on the affected window, and have him/her raise the window from that door, too. If it speeds up, you've found your problem.
'89 SSE - GX3 -190k, 155k on body - Back for another ride.