I really don't like the original 105E mounts. I started replacing them only to find brand new ones delaminating from day 1 after installation.
It is difficult to know where they have been made, and if the rubber is up to the job, and if the bonding has been done correctly. When I rebuilt my S2 I made a revised mount which I posted elsewhere on this site. See below.
I've used these since 2005. Serge has made a very similar mounts for his car.
Ideally the mount should be as soft as possible to absorb engine vibrations, yet it needs to be as stiff as possible, so the rear suspension isn't rolling all over the place with the engine. I opted for stiff, and had a very nice handling car.
Cheers
Richard