My experience with a programmer for a gas engine was for a Ford V10--really did nothing except cause me to have to use premium fuel to prevent preignition--most of the timers for gassers do little else but advance the spark timing, IMO.
Others have reported better results than I got;
2016 Tiffin 40 QBH
2015 38RSSA, traded
2005 TK3 #1869, 10 yrs of memories,
2017 F450 KR--one more Ford is it
2009 F450 4x4-died; 2010 F450-retired