akibonos. it's weird... i mean as stiff as my ride is.. that is.

 

Yeah, that sux. Given your setup, I assume yours isn't AWD. I probably should have mentioned that mine is the G37x sedan. I'm wondering how many people had this work performed already:

ITB11-019

G37 AWD; VIBRATION AND / OR BOOMING NOISE AT HIGHWAY SPEED

 

What exactly does that bulletin suggest is going to be adjusted or repaired?

 

It's transaxle related I believe. Seems like there's a spacer that gets inserted if yuo experience this vibration. I suppose there must have been a manufacturing defect in a few models, but it goes back to the '09s as well. Here's a link:

http://www.infinitig37.com/TSB/ITB11-019.pdf