The JTS only has two small cats built into the manifold/frontpipe ("maniverter").
I don't know where these other mythical 2 cats are coming from.
After the maniverter, there is a seperate flexi section. After this is bolted on something which looks like a silencer and is referred to as a "silenced catalyser" on eper, but personally I don't think it is a cat (it doesn't have a honeycombe structure inside, it is straight through, no baffles even) and I don't think it is necessary for the correct running of the car, as there are no lambda sensors after this so-called cat either.
If you really do need a replacement pair of front cats, I can supply good quality used ones in good working order (email me - firstname.lastname@example.org
The rest of the exhaust system you can just have made up if necessary, in stainless steel, for roughly £300 from your usual Powerflow/Longlife exhaust places.
I am not sure 100%, but you might be able to ditch the whole exhaust, manifold and all, and then fit a CF2 TS items.
The TS item has only one large cat so you should gain a few BHP as well.
I appreciate that the JTS has an additional lambda sensor, but it wouldn't take much to modify the exhaust for it to fit.
Anyone else done this?
The JTS engines don't run well at all without the cats, unless the car is remapped, and even then it has to be done by someone who really knows what they are doing, not just a generic remapper. There are 4 lambdas, two pre-cat and two post-cat, all in the combined manifold/front section. So you'd have to weld in 3 additional lambda bosses if you wanted to use 2.0 TS CF2 items. And I'm not sure they'd even clear the plastic water jacket that runs across the front of the 2.0 JTS engine.