tire pressure shouldn't make a difference. i would be looking at the quality of the wheel weight. most likely, the shop is not cleaning the rim properly before applying the stick-on weights. if the wheel is not cleaned then after a few days the weight is going to fall off. also, when applying the weights they need to be tapped ever so lightly with a plastic hammer to get the adhesive to bond evenly. drive your cars to pgh and i will hook you up :D