I haven’t looked online because I am not ordering one right now but the PP1 package includes the 3.55 gear for automatics. I’m not sure what you’re buying. I didn’t know it was available as a standalone option.
Yes, it is. My car had the 3.15's so that's what I have. If I were special ordering I would have gone for the 3.55's. I little more grunt on the low end would be worth the money. Also, if I recall, the 3.15's use a different housing and cannot be upgraded to 3.55's without changing it.
I ordered my 22’ with the 3.55’s(non Torsen)because I believe it comes with the iron housing instead of the aluminum. Mine will be drag raced and the aluminum housing has cracked at the mounting tabs for some folks.
For the A6 auto it was recommended to get them. For the A10 auto, however, it's not needed because of the A10's ratios and other features. It's been discussed already on this forum.