Idle Vibration especially on the intercooler

[SuprUsrStan]

I recently purchased a used F80 M3 and have been noticing a pesky bit of idle vibration coming through the 6MT and felt through the chair. Steering wheel and the rest of the car is pretty smooth, just shifter and chair. I don't remember the other M3's I test drove having vibration nearly this bad. It's only apparent when the car is idling at about 600 rpm. Anything above 800 and it goes away, regardless of AC on or off.

Popping open the hood, I can feel significant vibration coming from the top mount intercooler. I've read posts suggest that this could be from a bad spark plug. They were changed out at about 25,000 miles - about 6000 miles ago. I'm contemplating changing them out again myself.

Has anyone else had issues with vibration I'm describing attributed to a bad spark plug? On your cars, does the top mounted intercooler vibrate more than the rest of the engine? I feel like for some reason that particular part is the most severe vibration.