My 92TT ECU for undiagnosable reasons won't work with it. It also doesn't work with the Blitz R-VIT.
I've verified that both my R-VIT and BlaZt cable are working fine on other peoples' cars. Dammit. Oddly enough, the Techtom MDM100 does work on my car.
My understanding is that 90-93 have the CONSULT port.