Guess I forgot about a followup, but I did go to a mechanic to have the system flushed and since it have worked just fine 4 years later.......
Sorry for the delayed solution followup....

(azureblue, please "Thank" the users in this post you feel have helped you. Below is where you find it on a desktop, in mobile, it's in the dropdown menu in the same location. Sorry for the interruption, please continue... )

I suspect ignition coil, I have an 01 s60 and have had to replace mine when likewise ran horribly. Move to another cylinder the coil for the cylinder missing and see if the the miss moves with it

I would say those marks are from a prybar from someone checking for play in the lower control arms. you cannot get those marks from something rubbing in that spot. I would suggest looking for play in any and all front end components including engine mounts. Those are original Volvo LCA's, how many m...

but its not open. Where is the sensor or switch. ? This might be related to broken rear glass I had fixed last week. Maybe the repair guy disturbed something or glass got in the hatch panel. It may be related to the rear glass. Some cars, not mine, route the wire that's grounded when the tailgate i...

When I had a head gasket leak, there were bubbles in the coolant the whole time. It's interesting you have it only at 4k rpm. Maybe a small head gasket leak? Does your exhaust steam at 4k rpm. The test should show if they were exhaust gasses, but since it didnt, maybe the cooling system wasn't burpe...

The fault, ‘main beam (M/B) permanently on’: Been chasing this fault quite a while now, cleaned the indicator switch and it seemed to be fine after, but the fault returned about 3 weeks later. This time I knew it was the indicator switch, so this narrowed the search right down. The M/B’s went out if...

So, follow up, I had FCP Euro rush me a new set of Hutchinson engine mounts. And it appears to have solved the problem. I've only put 10 miles on it so far, but it seems to be very quiet again, no hint of that earthquake-like rumble. Strange thing, I had put an entirely new set of Hutchinson engine ...

I always drive 01 or 02 XC70 wagons. I've had problems with different tires wear patterns in pinches. The vibration is most certainly your tires. Especially if you've been messing with the suspension travel. If it got worse when you switched those tires then it's obviously your tires. CV joints usua...

if you have a scanner or torque app then i would say we need some details such as fuel trims (Long term). I do not suspect transmission issues here given the speed. I know some cars are particular about sparkplugs and personally have never used E3. I would stick Bosch iridiums or ngk iridiums as the...