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Try something simple first. Have your tires Road Force Balanced.
Anything when decelerating?
Only does it under load?
I'm going to assume everything suspension is tight, control arm bushings are in good shape, upper spring seats aren't torn. That sort of thing.
Could it be a transmission slipping/shuddering issue?
Axle or prop shaft is where I'd go. If I were diagnosing this at work (it would be easier for me) but I'd probably pop the prop shaft out and look at the front CV joint of it. Is it bound up? Drive it with the prop shaft out. If the vibration is gone, it is prop shaft or rear. If it is still there, it is something in the front.
Things I have seen that cause vibration under load at highway speed.
Missfires - typically have a pending code set but I have seen no flashing CEL/codes on some.
transmission slipping (this is uncommon for me to see in the flat land, but I've seen a few on cars that come from the mountains)
Prop shaft front CV joint seized. This usually causes a vibration that gets worse as speed increases. I have had more than a few that were only under a load though
Front axles. I haven't had to change many on XC90 and P2 chassis honestly. Unless the boot has been torn open for the last 6 years.
Rear axles usually cause a "pop" noise when turning under load. Only had one or two. Never a vibration under load.
AOC unit- usually vibrates if the tires are the wrong size, worn an excessive amount, different brands front to rear etc.
I had almost the exact same issue in my 06 Honda Odyssey. Ended up being one or both of the CV axles. Both axles seemed fine when I pulled then but after I test drove it with the new axles the van was back to normal.