2008 Challenger bogging down in turns and using excessive fuel :(

[jacques]

My 08 Challenger was running like a champ yesterday (towing skiers, wake boarders and a big tube). Today it gets up to speed fine going straight but lost 100 RPM, maxes out at 7700, yesterday it got to 7800 and losing power/bogged down in the turns. Only thing that changed was the fuel we added this morning (might be a red herring). The boat also seems to be burning fuel much more quickly. We added premium this afternoon with no apparent change in performance. Any advice welcome. Thanks!