The first decision tree branch: If you just sit parked and run engine RPMs up to 3500 and back down, does it induce any vibration? Can you rapidly build RPMs from idle to 3500 and have it be smooth? This is a way to detect (or rule out) imbalance that originates in the engine, or engine mount system.
Next, to rule out any transmission problem, you can go to a hilly area, and using the manual shifter, evaluate all 6 gears for vibration.
If it's a drivetrain problem, you can begin by jacking up the car to lift all 4 wheels off the ground. In neutral, engine off, manually rotate one wheel at a time to evaluate any hysteresis or clunking sound. In this test, you are inducing a "reflected" load torque on the axle/drivetrain. This sounds like the condition needed for vibration, e.g., there is no problem when coasting.
-------Oversized tires ------------------------------------------------
I've written elsewhere how putting oversized tires on a car overloads the drivetrain with excess reflected torque. See:
https://forums.swedespeed.com/showth...0-P3-2008-2016
2013 XC70 T6 Flamenco Red (hers)
2015 XC70 T6 Seashell Metallic (his)
past: 13 Volvos going back to '74 242 sedan
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