The only thing I upgraded was the rear diff housing with the larger bearing/angle chamge. The .1 have smaller bearing that would sometimes blow out. I ended up chewing my ring and pinion so I upgraded my diffs as well. Not really needed but I did it anyway...couple of months later, bought a .2. Now the .2 diff housing has had some problems with the plastic, Tekno is already on it. It's hit or miss on a good one or bad. Just a bad run of the plastic, so you can't tell by looking at it.

The lightened center drive shaft is really nice tho. Saves a lot of weight