What BruceLee is referring to, if I am not mistaken, is two different kinds of wheel balancing.
One is done "normally" by spinning the tire by the center of the rim the way you're probably used to seeing it done.
The other way, which is not that uncommon, is to balance the tire under a load or what he referred to as "dynamically".
I have heard that some Discount Tire stores have both kinds. That's the place you want to take your Boxster.
Another option is to call a few rim shops that specialize in high performance tires and rims... they have balancing equipment that goes up to and beyond 100 miles per hour.
I am told that wheel balancing problems go away after 90 mph or more. So, one very cheap fix for your problem is to drive faster!
Of course, one could become dangerous at high speeds or incur speeding tickets, so that may not be the best idea!
If my explanation requires correction and I'm not right on my descriptions, please do post it here so that I can learn more as well. I've NEVER been pleased with the balancing of my wheels since I bought my boxster last year... had them balanced three times and just decided to live with it.