To delete or not to delete ?

My BIL tried to license his deleted 08 RAM in Arizona and they rejected it after the mirror look under it and the EGR stuff missing under the hood with caps installed. And he failed to keep the deleted items given to him when he bought it. RAM/Cummins is coming out with a new system that is going to be completely down stream of the engine. No EGR. Any repair shop that is deleting truck is putting themselves up for large fines in the fed suits walk in.

Our son's major West Coast wholesale exhaust system supplier with not even stock delete pipes anymore.

It will all depend on what tune you use. I have two different EFI Live custom tunes and while both get better fuel mileage then stock, one gets noticeable better fuel economy than the other.

The one that gets better fuel mileage hardly ever goes past 1,600 rpm and will lug down to 950 rpm with the transmission tuning. The added power lower in the powerband allows for this. Another thing this tune does to conserve fuel is alter the VGT vanes to stay around half open cruising down the highway which is where VG turbos are most efficient. The tune that gets worse fuel mileage keeps me above 1,600 most of the time and the VGT is always around 30% while cruising down the road.

So if you decide to do it, research the proper tuner and ask plenty of questions. The right tuner can make a world of difference no only for fuel mileage, but also for reliability. There is also a myth that DEF trucks do not gain when deleting, but this is false.

A bud of mine has a 2012 Duramax deleted. We use it to go snowmobiling in the rockies in winter. It gets much better mpg deleted. Other than that it is really no noticeable difference in running and driving. The truck is probably the opposite of a fire truck. Its main use is interstate towing a light trailer. Very little city or idle time. He did have a sensor in def tank go bad, and I think a NoX sensor go bad as well.

Note, the exhaust is louder than stock. He left the Cat on and bought a quiet exhaust. Its not loud by any means, but its still louder than factory. Not loud enough to be annoying, but driving for 24 hrs straight with loud exhaust is not cool. Just a FYI.

Only do it if you want to deal with the legal issues. It is illegal to modify the manufacturer emissions systems. In Texas, and probably other states, it is illegal to sell a vehicle in which the emissions system has been "tampered with".

we had a 2016 Ford 6.7 deleted. Had to put stock exhaust back on.
Here in Manitoba Canada where we don't emission test, the gov figured out they can make great deal of ticket money on deleted Diesels and vehicles with catalytic converters removed.

In Manitoba they now have roadside checks with mirrors to see if you have you DPF on, if not it fails a safety and you tow it home until it can pass a new safety with the stock DPF back on.
The 2016 we had deleted, ran better and better mileage. We put the stock exhaust back on and sold it and went down to a F150. Our other 2016 F350 6.7 long box we use for camping has always had the stock exhaust and we are keeping it.

Now the locals are gutting out the stock exhaust and getting away with it that way.