Originally Posted by Maxhouse97

I have the same problem as RobC4SX51. I think it has to do with idle speed. When my engine is cold, after the fabspeed x-pipe was installed, my car idles at 640 rpm. This then causes the vibration. When the car is warm, idle raises closer to 800 rpm, and the vibration goes away.

So again I think it's not related to clamps or mounting. Lower back pressure and ecu tuning seems to make sense. Either that or the stock ECU adjusting for it eventually.

Originally Posted by 991carreradriver

I have the AWE system on my 2016 3.4L. I have slight vibration at idle, but not really pronounced. Interesting fact is that this system was on my 2014 3.4L and I did not notice any vibration whatsoever.
I plan to retorque when the weather gets warmer and see if that helps. The other difference is that I am Cobb tuned on the 2016, which may also be the cause. Personally, it does not really bother me.