Smoke machine vac leak diagnosis?

[Russianblue]

My current M54 runs perfectly other than an annoyingly low idle. I've had it checked for vacuum leaks but not sure they caught them.

It's not really throwing any codes, it just idles like 100-150 rpms lower than normal, probably around 600, at least compared to my previous M54, and there is a slight vibration with it that causes every manner of RATTLE inside the cabin. Door panel rattle, sunroof panel rattle, dash rattle. The rattles are small and irregular. Not everything rattles at the same time. And not all the time. The vibration is really pretty slight.

If I hold the brake and press the gas and get the idle up by 100rpms, the rattles disappear completely. There are ZERO rattles in neutral and park.

I do have a smoke machine but have never used it. What would be the best procedure to check for vac leaks with a smoke machine which would cover all potential problem spots?