If you have an imported 5 (Japanese import), up to 1995 is non-cat test, there are no exceptions.
For UK cars it is '92 cut-off, however following the MOT tester’s emissions flowchart it leads you to a section that states the car’s VIN must match a list of VINs for the emissions testing data, however Eunos Roadsters have no match, and if that is the case (which it always is for Eunos Roadsters) then by default the car must be put through a non-cat test. Emission limits on this are far higher, and physical presence of a cat is not required.
If the tester has an issue with this, quite simply they are wrong. Report them to the DVSA who will advise them that your vehicle does not need to be cat tested.