This seems to be a continual problem.
My understanding is this.
If a vehicle can't be exactly matched in the emissions database, then a non cat test should be performed.
This is the case for vehicles from 1st August 1992 to 31st July 1995.
For vehicles registered between 1st August 1995 to 31st August 2002 - same although use default limits.
There is a flow diagram, and it simply will direct you to the test to carry out.
http://www.motinfo.gov.uk/htdocs/m4s07000309.htm
UK Supra's will be in the database, and Japanese imports will not.
If an exact match cannot be determined by serial number, vin detail, engine number etc etc, a none catalytic convertor test should be performed or one within default limits based on year of manufacture.