8.2 Mercruiser MAG vs HO
 

I'm buying two pre owned 8.2 Mercruiser mags 380 HP. What is the difference between the standard and the HO? So far looking at part numbers, the only difference that I see is the little adapter that holds the flame arrestor. The ECU has the same part number, so I assume that it would have to be programmed to the HO's fueling, timing curve, if so, who can do this? Thanks!