[seenthelight!]

Yeah, he couldn't get the exact tyre size he wanted that were Audi specific, other than star marked ones designed for BMW.
The pulling would be caused by a significant difference in rolling diameter, and the vibration caused by the significant difference in weight - balancing just rectifies unequal patches of weight distribution and not overall weight difference between wheel/tyre setups. Hope this clarifies ..
Edit, also make sure that sets of tyres are manufactured on the same date, this will narrow down any discrepancies in weight/size if non starred. Tyres manufactured on the same production run are far likelier to be of similar spec, ie production run 1 in February could all be at the bottom limit of spec, production run 2 in March could all be at the top limit of spec. Therefore if you get a mix of February and March tyres, you will possibly have a set of tyres that are at opposite ends of manufacturing spec ..
As an engineer I have a bit of an insight on how manufacturing works ...