Several faults
 

So, today I chugged my way to a garage I know, who pointed me at another garage so I chugged there, smoke billowing out the back end. They diagnosed several faults:

1) Fuel Pressure
2) Air-flow sensor
3) Camshaft position sensor.

Can these be bought only from volvo, or from anywhere? It's a diesel. I have a spare fuel pump, but it's petrol - are they different? Anyone know anything?

Air flow sensors for the diesel are fairly common, I believe they are very expensive new from Volvo but there's plenty around in scrappers. Same ones as fitted to Renault Lagunas, Meganes and possibly the Renault Trafic / Vauxhall Vivaro / Nissan Primastar so there's some around at a good price.

Don't be tempted by a new aftermarket one as I found out the hard way they are crap. OE ones are Siemens branded.

A few too many sensors, to all fail at once. Have you checked the sensors fuse in the engine bay fuse box, to see if it is ok?

It wasn't quite all at once. I've been experiencing a flat spot during accelleration at precisely 2200 RPM, which has been progressively worsening. I'd been considering fuel pressure as a possibility, or MAF sensor. A couple of times it's cut out during hard accelleration on slip roads ever since I took possession. But I shall check the fuses now.

That is pretty much precisely the same fault I had when the MAF was at fault, and unplugging makes no difference