I'm sort of sorry for my last post, because it wasn't a productive one. Most of this has been debated quite at length ad nauseum in the past, and it actually does little good to rehash this topic again.
The info we have from Mehran, of course differs, and who was a dealer, and the main USA Distributor at the time the 4D was "supposedly" improved (2008).
I end with agreement with what Doug Deacon has said, and concur, that the Airy 3, Atmos, or UNIverse are all going to immensely please you, and to pick what fits your budget. Yes, if you pick the Airy 3 like I have, you may then regret not going even further up the ZYX line. Not that the Airy 3 lacks. But once you would live with a cartridge such as the Airy 3, you'll begin to wonder how can it get even better than this!?
I like the Airy 3 so much, trust me when I say I often think of ways how I can buy another one of these wonderful cartridges, and as well own the Atmos, or UNIverse before the opportunity of such good prices is gone. Mark