Looking at figures definately cat.
I have found some of the cheaper cats do tend to take a fair bit of warming up to get the figures down. Also Found that after a few good runs the cats seem to become more efficient almost like they have to be worn in a bit. Assuming this is due to manufacturing process leaving residue on honeycombe or something that need to be burnt of a bit before the cat works properly.
Is this the old type with just the underfloor cat or the later type with the one in the manifold and little one underneath?