It isn't the GP, granted, but I did go from OE hydraulic-filled rubber mounts on the Camaro to solid polyurethane and didn't notice harsh vibration at all. I did notice a bit more vibration and SOME additional noise, but now I'm not losing much power and torque due to soft mounts. And with the L36 slow-maro that I have, I need all the help I can get...for now. In the GP, I'm sticking with OE mounts to keep it all comfy and reasonably quiet for the family car that it is. The kids love to hear the CAI, HV3 and exhaust when in town and it lulls them to sleep out on the open road. Win-win for me and my wife!
