I have a 2006 GT that has a hesitation. This all started after changing the fuel filter due to a different type of hesitation that was cured by the filter change. The filter appeared to be original with 95,000 on it. I also put in new plugs at the same time, these were also the originals. I took a 300 mile trip with no issues after that. The problems I have now seem to have started after a WOT hit up to 6,000 rpm and the hesitation is worse once the engine is hot. I have replaced the Mass air sensor, it was bad according to the data. I have also cleaned the throttle body with the correct cleaner, it was REALLY bad. I cannot see any data on scanners that is showing any issue. I just had a mechanic friend of mine ride with me with his latest scanner and all he could see was bank one knock sensor activity when it hesitated. This could be anything causing it to run lean and knock but there are no misfires, real time or history. I want to put a tuner on this car but I need to have it right before I do so. Fuel pressure has also been checked with pids at 39.5 and actual at 29.5 Vacuum removed from fuel rail pressure sensor results in pid and actual of 40 lbs. running. At first turn of key actual fuel pressure hits 50 and if I hit the key a second time without starting it will hit 55lbs. Any suggestions are very much appreciated. I am a retired master tech and this kind of thing aggravates me because I know I am overlooking something.