After about a month of installing the poly mounts, I noticed a clunk like a lot of other people did on similar threads. I refused to go back to the foam mounts and just considered it the firmer mounts being the cause. Others on here just ended up replacing it back with foam.

At the shop there was one customer who was a bit too persistent about that knock and we took a closer look. The lower bushing is compressing a bit after some time and causing a visible gap. You push down and you can see and hear the gap move and go clunk. So, cut a poly in half and put that on top to clear out the gap. Seems to have shut it up. Just have to find a better way to cut them, though. Going to try it on my car next chance I get.

 

My independent in Norfolk/Virginia Beach did that with my rebuilt poly mounts. Didn't stay quiet once it got really cold (20*F). For the now really cheap price of the foam replacements, why bother? Either of the available replacements Mahle and URO are dirt cheap, change out in minutes, and the problem is over.

 

I thought having to do my MXD sway bar bushing mounts on my xkr every 10k miles is bad, but changing those Meyle or UROs on a non cats must be nice. But for CATS I'd have to constantly move bushings over, unless I want to spend $100 a mount. Not too feasible. But probably reasonable every oil change for non cats with those meyle mounts I guess