The people that make the DPF delete kits themselves say the best possible gain is 7%. With a tuner you may get a 10% gain. I calculated the probably payback on the cost and it was at around 75,000 miles to recover the cost of the changes.
I would not do it anyway as it is illegal and is wrong. Anyone remember that there is this strange concept of right and wrong. Wrong is changing your engine so the DPF no longer captures 99% of the soot from the engine and instead letting it out into the air. If that seems ethical then you might as well dispose of your household garbage by throwing it in the back of the truck and drive town the street with the tailgate open. You can save money on oil changes by dumping the oil into the gutter and into the sewers.
I remember in the 1970's when people were removing their catalytic converters so they did not have to buy unleaded gasoline. Now few people bother. With the truck fleet operators there is complete compliance with the laws. It is only the yahoo with the pickup who is too cheap and too thoughtless who removes emissions control equipment.
