As a Courtesy Infiniti rotated my tires on my I35 and now above 50mph there is an unacceptable vibration through the steering wheel. What can resolve this?

 

You might want to check that the lug nuts are all on w/at least 80ft/lbs of torque and/or you might want to make sure that the hubcentric rings, if you had them to begin with are still there. Those are the first things I would check for. When's the last time you had the wheels balanced?

 

unbolt and realign wheels to the hubs. Most likely one is not true.

 

+1, snug them up by hand and then torque them down.

Chris