MOT fail/pass

So Friday she sailed thru all the mech/electrical bits and fell at the emissions fence blowing the clean sheets since I acquired her. I had done the obligatory Italian tune up and had put fuel system cleaner thru the system before the winter lay up but to no avail. The MOT guy said CAT cleaner, hammer it over the weekend and try again Tues, this I duly did and tried not to drop under 4.5/5K on the revs and only rarely got into 3rd and bingo a pass. At my age I thought my boy racer days were long gone but I must say it was exhilarating, not sure a magistrate would agree though!
My prob appears to be my after market CAT can't cut it after only 3 years (original stolen) so what to do?  I was thinking about buying a new CAT for the next MOT hopefully get a pass then put the old one back until the next MOT, thoughts? Some might say this breaks the spirit of the law but me uselessly hammering around in circles this weekend has not exactly helped the environment.

Using a new cat’ for the test & getting that all important piece of paper was my plan & to pop the old (failure) one on for the rest of the year. For a couple of years all was well, until I didn’t have time to do the swap & chucked it in with fingers crossed. It sailed through.
Do I now have two good cat’s or two big disappointments waiting to happen.
M

Airportable wrote: Using a new cat’ for the test & getting that all important piece of paper was my plan & to pop the old (failure) one on for the rest of the year.  For a couple of years all was well, until I didn’t have time to do the swap & chucked it in with fingers crossed. It sailed through.
Do I now have two good cat’s or two big disappointments waiting to happen.
M

Cleaned and polished it today and took it for a leisurely run in the sun and it pops an EML, it did the same thing last year but that was just 200yds after the pass, I suspect I don't need a mechanic but an exorcist. Perhaps it's what the Stock Market calls a dead CAT bounce!!

Airportable did you get your CAT off of Schrodinger as he specialises in CAT's that are both dead and alive at the same time

Schroeder’s cat was as much a philosophical thought experiment as a physical cat in a box with some uranium & you can’t avoid the logic. However it doesn’t matter what you put in the box with the cat, unless it’s food you’re going to have a dead cat sooner or later. Deciding which catalytic converter (moving back to the correct terminology) is also a philosophical question; these days a good one is in danger of departing your car as a crap one & so have two, one for your MOT & the other to be sacrificed, or not, just like Schroeder’s cat.
M