I think it's the one about the choke that is broken off. It goes from the inlet manifold to the "sensor" on the inlet manifold then to the contraption mounted beside the accelerator lever. It's also broken on the spare engine that I have so I can't even use that.
Anyway the good news is that I have brought the camper home from my workshop (or man cave

. It hasn't pressurised the radiator as before and there is no coolant loss so all seems good. Before I changed the gasket it also missed a bit at a certain RPM but now it seems fine which is a bonus as well.
All in all it's cost me about £200 to change the gasket, timing belt, tensioner, plugs, filters, oil, and have the radiator recored. At least it'll be a good spare engine now when the time comes to change it for the bigger monster. What would a mechanic charge in labour to do the gasket??