EngineLabs said:"During testing, DFC Diesel observed fuel consumption reductions of 25 percent with factory tuning, an average of 5-percent increases in torque and horsepower, NOx reductions saw reductions as high as 80 percent, and the ability to extend oil change intervals jumped by 50 percent due to decreased soot and fuel dilution.
Other testing was completed in conjunction with Olsen Ecologic Lab in Fullerton, California to compare a stock Cummins 5.9-liter engine to one with a set of Speed of Air pistons installed. In that report, there was a 15.5-percent increase in horsepower and a 15.2-percent increase in torque. Testing also revealed Brake-Specific Fuel Consumption was reduced by 3.2 percent, particulate matter in the exhaust was reduced by 77.6 percent and NOx levels saw a reduction of 61 percent."

A New Diesel Piston That Increases Power And Reduces Emissions
Can an aftermarket diesel piston improve power and reduce emissions? According to Speed Of Air, it can and they designed it.