Mat is hardcore and has VWR solid 'Race' mounts and I have the VWR 'Fast Road' mounts. In my case the engine bay sounds transfer has not reduced over time. Surely BSH, VF, and VWR side engine mounts all transfer sounds from the engine bay just because there is less squishiness to soak it up. Doubtless part of the oem's side mounts function will be to reduce the engine bay sounds which exist.
It's one of those compromises like in suspension - Stiffer suspension gives a harder ride but gives benefits (if you want them).
