Firstly, the rear belt doesn't seem to want to centralize itself, when you spin the wheels a bit it always seems to want to slip a few mm off of the side of the rear pulley.. Does this mean something is not lined up properly? Or is this nothing to worry about?
Thanks.
Make sure the centering flanges of the pulleys are on opposite sides of the car. From memory on my car, the rear pulley flange is on the drivers side and the front pulley flange is on the passenger side. Very easy mistake to make,,,,,done it many times on many cars.