I'm not familiar with the predator. Did you return the programming to stock before tuning with the minimax? When you initially tuned with the minimax it should have gave you 2 tuning options. One with and one w/out emissions.
If you didn't return your truck to stock tuning before overwriting it with the minimax tunes limp mode could be maintained as a stored setting ( it's been a few year's since I've though about minimax and delete tuning. I had it on a deleted 2010 6.7L cummins I had)
I think these will be your only options. 1- find a dealer that is willing to work with you while you leave the exhaust as is, return the programming to "stock" (make sure that the minimax isn't vin locked before the dealer does anything) have them flash the pcm/ecm to return it to the original state, that should clear the limp mode. Then re-tune.
2-if a dealer isn't willing to completey work with you while deleted, return everything back to stock have them reflash the truck, drive it a bit make sure everything is good then delete it.
If you haven't already, join cumminsforum and ask their. You may get a better answer or the same. There isn't a ton of cummins guy's here.
2018 2500 6.4L Hemi Tradesman