I installed the RK Sport solid upper mount and lower mount in my wife's '03 Sunfire this afternoon. Couldn't stand the vibration, so I ripped them back out and reinstalled the stockers.
We've been searching for a replacement upper mount insert for the past few weeks with no luck whatsoever. Everywhere we go has the same part number listed, which is for a wedge shaped motor mount. I find it hard to believe that everyone out there has the wrong part number listed. We even took the car to the mechanic she was using before we got married and he ran into the same problem. As a last resort, we ponied up and bought the RK Sport kit.
The vibration was so violent inside the car I thought something was going to break.
I don't even want to see what they do on the Cobalt. I think I'll just buy the poly insert instead.

So, if anybody wants these stupid things, I'll sell them to ya for a little bit better deal than buying them new. P.M. me if you're interested.