No, I'm not one of the guys that preaches to get rid of it. I know everyone ha their reasons for deleting or not. But since you do still have it my idea of running the hottest tunes would do you no good in fact it would probably make it worse because your vehicle would probably regen more often.
correct, I run mine on the hd300 tuning with the hot setting ( 300hp ). Like I said though I don't drive it like a maniac but it sure is to nice to have some extra power when you need it. For towing I dial it down to the no power ( 50hp ) or mild ( 125hp ) settings.
I'm not familiar with that tuner but with my h&s I get the best mileage on the highest setting as long as I don't drive it like I stole it. Last tank that I figured out was 16.5mpg. About 85% highway and 15% town with a fair but of idling in between.
http://www.google.ca/url?sa=t&source=web&cd=2&ved=0CC8QFjAB&url=http%3A%2F%2Fwww.thedieselstop.com%2Fforums%2Ff54%2F08-f-350-door-pad-code-250839%2F&ei=6SZIUIH1DsSliQLzsIHIDA&usg=AFQjCNE1XpT__fgKVXv1g7lOafwcJG6CCA
I was going to try type it out but decided this was easier. Hopefully this helps.
I just realized that you said you already have a tuner installed. If you still have your dpf a tuner will just cause your truck to regen more often. If you are looking for a tuner that works well with the stock system banks makes a good one but I think it is fairly pricey. Also about the air...
Yes after you delete the dpf the truck is a little bit louder due to the fact that there will be no more restriction in the exhaust system. It will also smoke black if you give it a little to much throttle.
I originally went with an edge evolution but recently went with an h&s because I did an EGR delete and the edge did not support it. If you are planning on doing an EGR delete it would probably be worth it to just get a tuner that supports it right from the start because you may have trouble...
Mini maxx
Yes it uses the one before the turbo. If you install the mini and dpf delete tune the probes on the exhaust after the turbo are not needed anymore.
The xrt does not have gauges and I don't think it has shift on the fly capabilities. I could be wrong about the shift on the fly part. I was in the same boat and went with the mini and am very pleased with my decision. The unit is small but I have no problems seein the gauges.
The onboard computer is wrong. I don't believe he would be getting 24mpg. I am sure it improved a little though. Most people say 10-15%. What are you asking about the towing part of your question?