FGXR6T2013

Thanks for your comments. My car has done only 37000km. Does this make any difference? sometimes the vibration is there and sometime not

I have a vibration in my wheels at 55 km ph and a couple of other speeds. Its not wheels, alignment or balance. I have been told that it could be the harmonics in the exhaust and air flow through the breathing of the car. Done a CAI, Tune, High Flow Cat, 4 inch dump, stock exhaust. Looking at putting a Xforce 3.5 inch cat back exhaust on which might fix or move the vibration to a new speed. Just wondering if anyone else has had this issue and what you did to fix. Thanks 2013 XR6T