The real cause of injector rattle?

[Poodle]

Hdi thermostat opens at 83. If you want to bring combustion temperatures down getting a higher rated thermostat would help, but ideally you need to warm the inlet charge. Part of the function of the egr systems are to bring combustion temperatures down when cruising, they do it for emissions purposes, but the effect is the same. Tbh i'm not convinced it'll help all that much though.