If air isn't coming through it's the air flow that's clogged and flushing the coolant won't do much.

Now if air was coming through but there was little heat the coolant flush would be a reasonable thing to do.

Hope you get more answers, but it may not be easy to find fix. From memory When trying to start with the engine hot, do you hear the fuel pump priming ? The fuel pressure is a bit low, may look at the PEM for corrosion ($40 off Ebay). Not sure why it's dropping pressure overnight, maybe a leaky FPS ...

Had almost exact same issue with my 2001 xc70 but only on hot days above 25c. I think/hope mine was the purge valve, i also found and repaired a one way valve under the inlet manifold, i have tested the car after updating the purge valve (i had the old style unit) and so far so good but its winter n...

I recently did what it sounds like you’re about to embark on - cam & crank seals. I got everything disassembled & it was very evident that neither intake nor exhaust front cam seal were leaking and this was at around 283,000 miles. What I found the most significant source of the leak to be w...

And that was a big deterrent for me too - the cost of the new hubs. I guess at almost 300k miles the cost has spread itself out alright. I plan to keep this car in service for many more years, so I just had to cough it up. Its fuel mileage is wonderful, even with a stage 1 tune file in the ECM and i...

Ease them off if loose, add some anti seize, andretighten.

If they won’t move and there is no leak, leave them alone.

The cilinder head should be okay then and only the manifold needs resurfacing? From what I read this is not a small job removing the manifold. Yes, only manifold. You can also just put a new set of gaskets and studs+nuts, they will buy you for some time to source a donor manifold and resurface it. ...

Correct: the front half of the rear final drive is an electronic clutch type mechanism that requires Genuine Volvo AOC oil, link here - https://www.fcpeuro.com/products/volvo-aoc-haldex-gear-oil-1-liter-31325136 The rear half is your ring and pinion gear and requires nothing special, just synthetic ...

Gauge is correct. VIDA aid probably calculating pressure based on PEM duty cycle.

Have you opened up PEM and had a look inside ?

In the XC90 forum there are some links I found to PEM waveform troubleshooting , user shockwave and I used these to sort out a fuel delivery problem a few years back.