Help!!! My Mondeo V6 go through the horses again and again!

Hello, I have a big problem with my Mondeo V6 (170hp, year 99, tournament, Giha, 70,000 KM): At irregular intervals especially in the range over 1800 1/min the speed does not go down or strongly delayed. The problem occurs suddenly and without recognizable connection. If I take the foot then from the accelerator pedal, it does not go into thrust operation, but the speed remains. (No, I have no cruise control :-)) If I also hit the clutch, the rotary fence rises. l slowly on – so around 500-1000 1/min, lasts about 4-5 seconds and then falls quite slowly. Makes a great impression at the traffic light :/. The condition lasts differently for a long time, and then disappears again without recognizable influences. First the speed no longer increases when uncoupled, but remains “hanging”, then it falls slowly, and finally again quite normal. I had this in a weakened form already before quite exactly a year ago. At that time I was with it 4x in total at Ford. Each time of course with demonstration effect 🙁 Say: error did not occur! For the sake of caution they changed the throttle flap pot and later the air quantity meter???. After that 4 months was quiet, then it still occurred 2-3x quite isolated, but now it happens almost every 2nd ride. Well, warranty has now expired and really did not find the error even after 4 dates… That means for me that I now myself Have any of you ever had this rehearsal, or at least an idea, where the problem lies? Rejoice me over every tip. Thank you so much, Hainereiner