i had kind of an issue. My steering wheel was vibrating after 50 mph.
After some investigations (checked engine, transmission) turned out that one of my wheels had a little deformation (2-4mm) after i got into a big whole (pit) on speed. The rim got a little deformation not noticable for eye. it is seen only on special balancing hardware.
Check the rims dude

 

might be from irregular tire pressure on all four corners also.