2010 xkr with 100k miles

am getting a strange engine vibration between 3-4.5k rpm in every gear at all speeds (as low as 10mph - 70mph).

anyone know what this might be?
Almost feels like out of balance tires but coming from the engine and I s not speed related

bad tires?
bad engine or trans mount?
old spark plugs?
something with supercharger?

 

5L V8, timing chain tensioners. It's why I keep telling people stop buying these - especially the earlier models

 

engine mounts are always broken on these, emergency strap just does a good job making sure it doesn’t jump around and hit stuff

 

I flew an American Gruman airplane where in the instructions read, not to let the engine run continuously in a shortrange range of RPM! Just to pass thru that range.