Have you fitted any egr blank or egr restrictor to this engine? I tried that and the engine hot hotter so I removed it. If you need an egr valve I have a newish one you can have cheap, so don't chuck money at a new one as they are expensive.
The thermostat might be the best route to test first, as it could be partially stuck open. Mind you on this engine by ye time you've got to the thermostat, you might as well put a new (tested) one in.