Polyurethane replacement bushings are not good. Sure they decrease suspension movement ergo better handling somewhat. The bad point of urethane is it does not like to give easily. Its important for suspension geometry to be able to pivot on this trailing arm bushing. Pivoting means this connecting needs to be rubber. The REAL problem come in when your trying to race this this type of bushing. In hard cornering the Urethane is said to have snap oversteer due to incorrect suspension geometry caused by the lack of needed flexability.
The only correct way to replace this rear trailing arm bushings problem is to buy oem, or megan race bushing which are made from a harder rubber. Don't cheap out man the T/A bushing is an important needed peice to keep the ass end predictable.
