16G's still keep up with everything known to man. If you already have the kit keep it. I had the TD05-16G kit on my last Z and still have the kit sitting in my garage to put on my new one. Every dyno chart I've seen and every other car I've driven still doesn't show me anything that would convince me that they are any better. If you already have the Greddy kit there is NO reason to think it's an upgrade to get GT's. GT Ball bearings are not the end all save all. Sure they are nice, non rebuildable, and cost a little more.....oh wait only nice, but there isn't that much difference in the two. It's very little gain. Granted, I already own the kit so no reason to waste money. If I didn't own it I would entertain the thought of something else because of initial cost. The new Borg's may change my mind but that remains to be seen.