450 diamond not making WOT RPM intermittently

Hello, nice to be part of the forum. I have a pair of 450 diamonds, the have 1000hrs and Tony’s double filter set up with gauges. Recently purchased the boat and floated her 2500miles from Ohio to key west. When we departed I briefly hit WOT and saw 2625rpm. During the later parts of the trip I noticed intermittent hesitation to get over the hump. It always got there, then ran flawless at 2250rpm making 21knots. More recently the problem is happening more often, and I now can reach max 2400 rpm. My rpm and cruising speed is still the exact same (21 knots@2250). The bottom is clean, and the boat is actually lighter then it was when we departed Ohio. Here is a list of what maintenance has been done since arriving to Florida; all (6) fuel filters, cleaned air fileters, oil, oil filters, trans oil, aftercoolers cleaned and pressure checked, turbo lines/ hoses pressure checked. Any input is greatly appreciated.