Silicon coming off in a 911 chrome wheel?

I am posting this message for my brother so I will do my best to describe what is happening to his 2001 Turbo. He started to feel a shake in the front tires at about 65 mph a week ago. He took it to a reputable tire/wheel shop (we have done business there for 18 years) and they told him he needed new tires on the front. We did ask if the wheel was "true" and they did tell us yes. After the new tires were put on he still had the problem. They now say that it seems like something has come loose in the wheel. They still say that it rolls true but something is inside the wheel making the problem. My brother called the place where he bought the wheel from and they said when they chrome the wheel they put silicon in the wheel (?) and that may be the problem.

Has anyone heard of this before? Does he need to buy a new chrome rim to fix the problem?

Sorry for the long and not very detailed post, but any help would be appreciated.

 

Thanks for the help...anyone with some real thought's on this problem?