I've got a feeling it may have the special Alfa port - it's not OBD2, it needs special software like alfadiag or alfaobd to read it. EU requirements for OBD2 didn't come in until 2001 for petrol, 2004 for diesel and I don't think Alfa adopted it until required to.
Does it need to be standard OBD2, or can you get away with showing it has on-board diagnostics via an accessible port and you can read fault codes, etc? If it's the latter you should be OK.
alfaowner.com may be a better place to ask.