I can't think anything that links all the symptoms together:
- low pitched rumble I associate with wheel bearings, tyres or exhaust,
- if previous work on the turbo improved the noise for a while than that has got to be the obvious suspect, though I don't understand why,
- neither of the above would cause high engine temperatures.
Frankly I am at a loss to explain the problem unless there is more than one fault i.e. the noise is unrelated to the temperature. Perhaps somebody else can chip in with an explanation.