If you're plan to do the deletes and put on a tuner, it will leave telltale signs that the emission system has been altered, even if you put everything back to its original configuration. So if a service department wants to be picky, they'll know it was deleted and could easily deny warranty work.
If you're in an area that does annual or semi-annual emissions checks, it'll have to be put back to its original state before the inspection, and it still might not pass if codes come up when they check.
And lastly, doing deletes (or any tampering with emissions systems) is a federal offense. A lot of people get away with it, but who knows for how long?
I'm not trying to talk you out of, or into anything. Just pointing out a few things I learned during the year I had my 2010 2500 Ram CTD. I switched to a 2011 Hemi, and found I get as good of mileage towing my 6000# plus travel trailer (10-12 mpg), and much better mileage when not carrying a load (20 more or less, compared to 15-17mpg, all stock).
Bill