So there is an audible vacuum leak in my brother's V40. Listening for the whistle I found that it's at the fuel pressure regulator. The vacuum elbows are too brittle to be removed without destroying them, but otherwise they don't seem to be leaking - the leak appears to be actually between the ...

Problem solved by adjusting the wastegate preload a couple of turns. Turns out it was opening almost immediately when any pressure was applied (the wastegate arm could actually be moved a little bit by hand).
I'm assuming as there was little to no preload on the wastegate arm, the valve inside the ...

I think the immobilizer just cuts out the ignition several seconds after the key is turned if it doesn't get a RFID read from the key, regardless whether the engine is running or not. Though I am still not sure what the flashing red light in the middle of the dashboard meant.

The no-start issue seems to have been solved by unplugging and re-plugging the antenna ring. We'll see how it holds up during cold weather.
Though I think it might be useful to others that it appears the immobilizer kicks in several seconds after the ignition is first set. That means, if you ...

OK. Replaced the mount. Obviously, the new one was interfering with the bracket so much that it was impossible to install. However, on my mount the metal plate was attached with two tiny screws (I have no idea what the plate originally is for), so I unscrewed them and rotated the plate around. Then ...

Wow, great suggestion! I'll mod my switch this way too.

I've read one other post suggesting checking your lower engine mount as a drooping engine could cause the bracket to touch.

In my car the tabs that hold the switch together broke so the inside part is not held in tight enough against the housing. Probably the same issue you're facing. That volvo plastic gets really brittle after 15 years.

My car (2001 C70 T5) has a shot upper engine mount, OEM 8649597.
i.e.
http://www.skandix.de/en/spare-parts/engine/engine-mountings/engine-mounting-upper/1029703/

It seems to me that the updated square style mount (30680770) should be interchangeable with this model, even though the site says it's ...

Mine's a turbo so there's quite a bit of pipework under the hood, though I'll give it a shot. Though for now I'll start tearing the steering column apart and inspecting the antenna ring. I've had intermittent issues with it before.