The real cause of injector rattle?

[pug306driver]

so  the cooling system heater plugs turn off and on whilst driving, temperature dependant?

Since a gate  stat was fitted some time ago our estate sits at 80 on the gauge for steady driving, i have removed both cooling system heater plug fuses and relays just after xmas and all seems ok, i removed them because the relay socket and relay nearest the heater plugs showed overheating signs, melted plastic, but the other one, furthest from the engine seemed all ok.

sometimes after a run and she is idleing at home she sounds real sweet, and others a little clattery, injectors or egr??