Vibration at 80 kph is definately balancing, espically if the tires were already on the rims, the guy probably assumed they were fine and just put them on. I had the exact same thing last year. When you get up to speed on the highway the steering wheel begins to shake, then disappear at 120kmh. Have them double check it, espically if they mechanic who took them off didn't mark on the tire which one came from which wheel. And beyond that, you've done some driving without them on so you've changed your car slightly. Always balance your tires, and yes they will probably make more "noise" as it is a more aggresive tire, but the vibration shouldnt be there.