With that little mileage on the damper, I wouldn't suspect that is the culprit, unless it is defective.
Cap'n could be on to something...wheel bent/curbed, etc.
But, you have chrome 15-hole MB wheels, right? This could be your "very slight" vibration problem. I have several friends with chrome MB wheels as well as chrome aftermarket wheels and they complain of the same problem (frustrating and expensive). As the chrome process is a "coating" (up to three layers), it is likely difficult to get a perfectly uniform layer(s). Also, if you are using stick on weights, this could contribute as well.
p.s. What led you to your decision to pop for the Michelins?