Diesel engine chip?

$1,100 for a LML delete tune... no thanks

Btw you'll get a ton of responses here telling you that tuning your truck will destroy it.
Yes you can roast a stock transmission with stupid use of aftermarket hp but if use judiciously there are many benefits and little downside provided warranty or emissions testing aren't a priority.
I've not tuned and long term operated any dpf or scr emissions trucks but many have. Same basic platforms as pre 2008 trucks, 2 of which, a Dmax LB7 and a CR Cummins I've put many miles on with healthy tunes. In over 250kmi between the 2 trucks it's cost me a new clutch in the Dodge but that is a known very weak link in those trucks anyway. Otherwise I enjoy the stump pulling power that 900+ ft lbs in an otherwise stock vehicle gives.
Disclaimer, this stuff is not idiot proof like the warning to not plug your toaster in in the bath tub. Without some basic understanding at a minimum your right foot can break stuff!

Go check out a Dmax forum for better info.
You basically have 3 options.
1. Leave it stock
2. Add an emissions compatible tuner or program. Won't help much w mileage but will give more power at the expense of voiding warranty while making the scr work overtime to get rid of additional soot from the additional fuel.
3. Delete the emissions system for better mileage and clean running truck at the expense of both warranty and in ability to send he truck thru emissions testing without returning it to stock. Both tune and hard parts.

Don't go 'Canned' tune. Get EFI-Live.

There are tuners designed to be used with DPF intact and tuners designed to work only with the DPF removed and generally say something like "for off highway race use only". Any removal of the DPF system could pose a big problem if you have emissions testing in your area. I spend a good bit of time on the Dodge Cummins Diesel forum. It looks to me like a high percentage of the folks reporting big problems are driving trucks with tuners. I realize many people that tune their trucks drive them hard. I know people that have tuned their trucks with no problems for many miles (no emissions testing here), but I think the best chance for getting the truck to go high miles with minimal issues is keeping it stock. Good luck. Keith