Just a quick "after action review...
I had the local shop that pressed in the motor mount use the same alignment as the old one (based on the bolt-holes). They were pretty busy and ultimately did it for no-charge after about a week. When I went to install the matching shims that I also got from Pelican, I discovered that they didn't align correctly on the motor mount holder.
So in the picture above -- with the old motor mount in the holder, the shims would have been installed with the long end towards the right. When I had the new motor mount installed in the holder, and went to put on the shims, they now had the long side to the left. It was the
only way that they could fit on the core of the mount (but they now interfered with the small flange that you can see toward the top center of the picture)
Hmmmm...
I wasn't going to take the mount back and pester the shop that did me the favor a second time, and I wanted to get the car back on the road and out of the garage so I finished the installation for now using the hold shims, which were trimmed to fit the new mount.
Results? A definite improvement, especially at the 4000 RPM plus zone of the rev range where the car used to have a significant rumble. But -- I can still hear the rumble there, but it is about 80% subdued.
Theories?
1) At some point the mount had been replaced and installed up-side down prior to my purchase of the car.
2) Even though the arrangement of the rubber in the mount is similar in both versions, Porsche for whatever reason decided to now align the 987 mounts 180-degrees from the 986 mounts.
I suspect that the 2nd theory may be correct. I'm planning on getting a lift this winter and then I'll go back and pull the mount again and have the alignment flipped to match the new shims. I suspect that they will change the frequency of the mount in the 4000 RPM range and quiet the residual boom that still remains.
I'll post the results after I do that.