I would use the 100 ron from Shell, because it has ethonol and it may help.
The last time I took a car for enissions test , this fuel wasn't available so I used normal 98 ron.
If you can get your hands on a new ( or near new) compliance cat , i would use that as well .
To be honest with you , I dont like your chances with your current set up. If I remember correct your car is 95 model and that mekes it harder, earlier models would be slightly easier to pass.
Good luck and let us know how you go. Give me a buz if you like as I have a tip fpr you but I dont want to put it on here for obvious reasons .