Exhaust Replacement On A 1991 Eunos

[HereBeMonsters]

Having a bit of a nightmare trying to buy a 1991 Eunos from a dealer in Gloucestershire. Latest thing is it has failed the MOT on emissions. They claim it needs a new exhaust with a new cat in it. I reckon it doesn't need a cat as it's too old, but they say it does as it had one from the factory.
Reckon it would be alright with a new "standard" exhaust or is it best to have the cat as well? How much power does the cat sap from the 1.6? Is it usual to fail on emissions if the cat is knackered? It's a cheap car, and I will be getting the engine rebuilt for a supercharger conversion in the winter, but I just want it to last through the summer really.

[MX-5 Lazza]

A '91 Eunos doesn't need a cat as long as it's got Eunos Roadster on the reg document and not Mazda Roadster.
Even then I doubt the cat will be shot unless you can hear the cat rattling. More likely that the O2 and/or engine temp sensors are faulty.

[sidewaysste]

It doesn't matter if it's an import or a uk car, pre '92 it doesn't need a cat for the MOT. the cat could well be on its way out - we're seeing more and more of them fail