I don't know for sure as I have already stated I keep mine attached, but with the ability to shift power levels on the fly, I don't see how the MiniMaxx isn't needed. I am certain my truck runs differently on stock vs. performance and I can change that at will with the MM attached. I'm pretty certain it tells the truck to just run at stock with emissions by passed when the Minimaxx is removed. This is confirmed by page 57 of my MM manual. This applies to 2011-2012 owners only.
RIP Paul Hill Hdslider June 6th 1955-May 28th 2014
I miss you my friend