The NG900's 94-98 did not have in-key immobilizers. That is, the keys for the 94-98 900's did not have a little chip in them. Instead, the alarm ecu disables the fuel pump, starter, and ignition when the alarm is engaged. The newer 9-3's from 99 have the same ecu immobilization features PLUS the in-key immobilizer chip. Hope this helps.
Lawrence
Lawrence