Major Vibration Issues - Help

NOBLE|370Z

Folks

Today I went for a nice calm spin around town. After about an hour of driving suddenly when cruising at 80km/hr my car began to vibrate significantly. There is a deep bass sound that goes in and out with high frequency. It's more noticeably after a take off the gas and coast. When I give it throttle, it goes away mostly. Therefore, I believe that it is something rotational. I don't believe it's the engine, or the wheels/suspension. When I pulled over to stop, I gave the car a few revs for a couple of minutes, and the vibration was not present. I had an alignment done on my car recently as well, so I don't believe it's the wheels.

My 370Z MT TT has been boosted for about 10,000km. Due to the OEM clutch slipping on me, recently I upgraded it about 1000km ago. I went through Joe at Z Speed Performance and bought/installed the Southbend complete stage 3 clutch package. I have a feeling that the vibration has to do with the clutch...

The reason why I think so is that I read a recent thread here by JoePro that outlined a problem with a similar vibration issue, and he was able to conclude that the new pressure plate on his southbend clutch kit broke. However, when I compare the symptoms between his experience and mine, I notice that his car vibrated when it was parked or up on a lift. Therefore, the issue may still be outstanding here...

There has only been one other event that may be linked to this. About 80km ago, I was pushing the car hard (10psi), and when I let off the throttle to slow down there was an immediate bang sound, which I believed was only backfire. Other than needing to update my tune, I don't think that has anything to do with this. If I broke the motor, then I'm sure the ECU would have thrown a code by now...

Does anyone have any idea what is going on? I appreciate your feedback.