Really interested to hear what you found! Chasing the same issue today on my '05 XC90 2.5T and I've even done the same as you, moving coils, plugs, etc. I haven't noticed cracked wires, but after a bad breather pipe, and oil everywhere, I wouldn't be surprised the insulation could be deteriorated ...

Thanks, Wellington! You've given me a lot to look for!

Same here! I'll be checking back to see if you learn anything. I have a 2005 T5 XC90, and it's been dying on idle, jolting on hills and during accel, and even dying right as I start it.
I plan to get into it and check hoses and connections. I've had a bit of an oil leak around the oil cap, causing ...