Its mandatory from what i know. It is the only way to demand enough fluid psi inside the trans.
I had it when i had my minimaxx and loved it. I just didnt care for the abusive ecm tunes that was noisy, smokey, and made things pop.
The least expensive way to get it is a XRT with just the trans software.
Do a search for Revmax or find Dave Matthews on cumminsforum.com, he seems to be real good with passing on information and getting answers.
As far as efi, i use Zach at Starlight Diesel. There are a lot of good tuners on here though.
A few: efibyryan.com, doghousediesel.com, cumminstuner.com, ...etc
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