Had the windshield on the wife's touring replaced the other day. I was out there chatting with the installer and talking about the old racer's trick of using window weld to fill gaps in rubber mounts to add stiffness.

Realized that I already had the passenger engine mount off to install the headers, so I popped into the garage and pulled the driver's side too.

Dude let me borrow his goop gun and 5 minutes later I had basically turned my relatively new non-m mounts (fluid filled rubber w air gap) into m3 mounts (fluid filled solid rubber). Gave them a few days to cure before reinstalling. Free upgrade!