ALVO360I'd expect a partially blocked cat would show itself when you open up the throttle and you'd notice your down on power. I recently fixed a rough start condition by changing the Fuel pressure regulator and It was showing within spec pressure when I tested it. I'm not sure what the story was there, but it worked.
Can you just pull the cold start injector and the injectors out of the manifold and prime the pump to check for leaks?
Chasing gremlins like this can be a nightmare. I empathise with you. But it usually leads to a 'refresh' of components and a greater understanding of your machine, so it's not all bad. I hope you managed to sort this out.
Thanks for the feedback @ALVO360 Yep, more work to do and more things to look at. At the moment we’re having to use it for any drives beyond range of the EV as I have the front axle out of the C30 awaiting a tool. Once the C30 is back together I can spend a bit more time on the 240 whether it be swapping out parts with the other engine I have on hand or testing the injectors etc.