I think its to do with the material that the poly bushes are made from that increases the vibration - They don't bend as much as regular rubber bushings, so they aren't as flexible. The stiffer poly bush would be good for the likes of control arms for example, but as I said previously, I wouldn't use them in a torque mount.
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2007 S80 2.4 D5 - 110,000 miles
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