Mine was set at 750 rpm. Now it's memorised at 800 rpm, even after a battery change.
And it's a clear improvement in the overall functioning of the motor.

Another vibration issue, 2.2 160 bhp 4wd with 120,000 miles.
Cambelt and tensioners / idlers changed at 100K, 2 years ago and no issues since.
All transmission fluids changed at 100k also including haldex filter and pump cleaned out, no issues since.

Vibration at idle appeared a few weeks ago, not sure when as I don't drive the car daily. Checked codes, nothing jumping out as a potential. Definitely feels like a mechanical out of balance and just looking at the engine mounts, the gearbox side mount was definitely moving a lot more than the belt side. It almost felt like a misfire so I did a return leak back check on the injectors. Sure enough, one injector was showing 3 times the others at idle. Got a new injector, replaced the fuel filter at the same time and, no change. Began to worry that there was a bigger problem internally so took off the inlet manifold and the glow plugs and did a compression test, all good. Inlet manifold and throttle body cleaned while it was all apart and rebuilt, no change so did a longer leak check and found that two more injectors were showing around double the leakage of the new one, the third was a bit higher but decided to change the remaining 3 injectors in any case. No change.
I've run the engine with the auxiliary belt removed, no change. Also have checked the pulley operation and it is still working correctly so I've ruled that out.
Since I was running out of options, I decided to change the gearbox side mounting as that one the one with the most movement and it can be felt much more in the passenger seat (gearbox side) than the driver's side. No change.
I'm now thinking that this is a DMF fault with perhaps one of the weights not returning to the idle position. However, there are no rattles coming from the bellhousing and the clutch operation and bite is fine so I don't really want to pull the gearbox / subframe / transfer box out only to find that the issue lies somewhere else.

Any other suggestions?