My replacement definitely didn't help vibration, in fact the new firmer rubber might be causing more vibration at idle. But the drivetrain does seem to be more direct when shifting which is nice.
Also the new alloy kind.
I'm not sure the other three come in the alloy? In fact, having just done the tranny to strut-tower one on the drivers side under the intake, I can tell you that one is definitely not light alloy.
Brian
99 SVT