you still have not posted year, make model..

i would want to know how much time on the dyno did they take to do the EGR delete REMAP..

atmosphere contains only 21% oxygen. only oxygen combusts with fuel.

during normal operation with an EGR .. the exhaust flow allowed into the intake proportionally.. contains much less than 21% oxygen.. so the fuel needs are reduced because of the reduction in oxygen available for combustion.

so a an engine running EGR actually can get increased fuel economy.

there are issues on some diesel engines that clog the EGR devices.. the egr coolers .. the egr passages. this can make engines run bad because of the clogging.

without EGR flow.. there will be too much oxygen for the amount of fuel the computer is dispensing.. so the engine runs hot.. pings. has reduced power.. pistons and rings will be overheated and usually scuff the piston skirts on the cylinder walls.. ripping the skirts off as they melt and transfer weld to the cylinders.. the aluminum rolls up under the rings and lifts them off the cylinder walls allowing compression and combustion gasses to go past..

combustion gases without egr are well above 2600F under load. aluminum melts at 1000F.

its so amazing to drive down the long beach freeway following 100 or more trucks and not smelling any diesel exhaust..