I ran one in the 10s for years but it also was only 5ish years old too. Assuming you are talking a fox body then I might question any stock balancer regardless of power levels just due to age/use by now. I know the one on my brothers 93 GT failed in recent years.
I had a stock, original balancer on my HCI Nitrous C4 car. Ran high 6's/7.0s for years. Eventually the rubber failed and started hitting the oil pan (sounded like a knock). Put another stock one on, and it's been fine since. They do fail, but hold up better than a lot of people think.
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