The Euroflo was on the car since August 2015. The back box fitted better than the Klarius version I fitted the year before. The Euroflo system looks more like the original than the React/Klarius combo, I bought from Euro Car Parts. The both brands come with stainless steel catalytic converter sections. The shapes differ. I actual have a used React Cat' for a Mk1. I will sell that as it is mint.
Here is a picture after cutting off the corroded bolts. Original Mk1 back box joint after 17 years.
The issue is the fit. Make sure it is not touching anything, and that is aligned and not transmitting any resonance.
The Mk2 "should" be easier, but you never know what to expect. I sold my Mk1 a few months back. Hopefully I should not need to touch the Mk3 yet.
There is a lot of reading and even though your car is different the principals are the same. A friend had a new back box fitted on his Mk2, and it seemed fine.