Steering wheel vibration at 80 mph is a common problem with the M3. The car is very sensitive at that speed. I always make sure I have the wheels / tires road force balanced, torque the lugs with the wheels in the air or with only slight weight on them (front wheels are hard to torque without lowering the car to the point that the tire touches the ground slightly), and of course have them test the wheels / tires for bends and run-out. Unfortunately I have experienced slight vibration even when all of the above listed things are done right. Sometimes it's paranoia on my part and really only due to the road surface. Make sure you are on a very smooth road to test. The M3 is designed to have excellent road feel which translates into road surface imperfections transmitting to the steering wheel.
'08 E90 M3 - Alpine White - Sold
'13 E92 M3 - Silverstone II - Sold
'04 E46 M3 - Jet Black - BBS E88, KW Clubsports, Brembo BBK, SuperSprint Exhaust