[northernblue]

If you have'nt tried it yet , take the oil filler cap off with the engine running,if it sounds like a tug boat then you have a vacuum leak.
If this happens crimp the engine mount hoses to see if the engine goes quiet.one by one.

Big thanks to CheshireD5 for this , my rear mount is knackered but now blanked off till i can sort it.
Just come back from Great Yarmouth towing a caravan with no ESR ,i reckon the turbo needed it.