the issue is still the same OBD1->OBD2 as the wiring is not a direct fit custom wiring harness is needed also the 91 lacks OBD2 sensors such as fuel tank pressure and EVAP system is diffrent this is not a simple swap unless you cut corners like use a OBD1 computer and have it chipped or a OBD1 prelude Vtec (H22) ECU.