ok guys. i think that everyone needs to check this out.
i replaced my balancer today. the entire rubber was broken out. GM has redesigned the replacement balancer. the rubber is no where near as wide as the old one , giving it more stablilty. it wont fly off when it breaks the rubber. i would have to say that is was going for some time. this also could have been some of the knock retard i was getting too. then when it wore enough of the rubber out, then it rattled, also moving the balance point too. i got the balancer for 129 bux. the old balancer, the rubber ring was aprox 1" thick. the new one is maybe 3/16-1/4" thick. almost like a small block chev. balancer.
if you have time and a series 1 motor, please check your balancer. the local part store i go too for speed parts, the guy that owns it has a 2002 impala, fully decked out. he has other 3.8 cars too. he told me tonight that he has had like 5 cars that he had to replace the balancer on due to this.