Is it turbo or not?

A turbo issue does not cause a engine to shake violently and die so no.

Sounds like more of a fuel issue

 

Could the turbo prevent air getting to the intake manifold?

 

Yes, it is possible. I have little Volvo engine experience, but it's actually fairly common on a Cummins for the turbo to stick closed and shut the engine down. On a Cummins, the turbo is shut to add exhaust braking to the jakes. So this usually happens after going down hill using the jakes. When they stick closed, it'll try to fire, but the exhaust has nowhere to go and it just builds up pressure, shutters and won't run. The shutter can be somewhat violent. Many times, when the actuator is pulled, the turbo moves smooth and a new actuator fixes the issue. Other times the whole turbo needs to be replaced.

I cannot say for sure that Volvo engines have the same issue, I'm just saying that what they are telling you is plausable.

 

I had a old Volvo with a brake in the exhaust pipe after turbo.
That rig was a pita during a cold, subzero, start.
Couldn't use ether, the intake had heaters in the intake.
I had to spray pb blaster on it turn something with a wrench. Pry on something else. Had to loosen the exhaust strap to let the exhaust out. It would build pressure.

Man I would cuss at it, and the darn motor would cuss right back until it warmed up.

I knew what to do to start truck.
Now I know technically what was happening.
Thanks