[moberegger]

From Out of the Park Developments Online Manuals

Gap Power is a measure of how much power a player has to the gaps - the places in the outfield between the left fielder and center fielder, and between the center fielder and right fielder. Gap Power directly affects the number of doubles and triples a player hits. Gap Power, however, has no direct effect on home runs, or on the likelihood that a player will make contact.

So, the way I understand it, Gap Power has nothing to do with home runs, but is related to BABIP. A player could have many home runs, but a low BABIP.