Okay, so I am looking at these and wondering, do I need this? What are the pros for this item? What's wrong with the stock ones? Do you tthink I should upgrade to soild differential mounts from the liquid filled stock units? I heard the soild ones reduce wheel hop but is this a good investment for reliability/drift performance?
They're about $120

 

pros - better handling, stiffer
negative - stiffer, you will hear diff gear noise

I assume for $120 you are looking at metal, you can also go with a stiff plastic to save cost.
www.mmr-direct.com

 

No, i was looking at a plastic one with a metal insert from rx7.com. Okay, so these don't need to be replaced if I want reliability?

 

Replace them only if you want to, if you want better handling, or if yours are shot.