98 ford expedition 4.6l. having some issues with loss of power and surging like and sounded like misfire. No engine light on at all.you could floor it and it wouldnt take off. Had a long block put in 3 years ago. Egr not too long ago, replaced ignition coils and just was told it was the converters then the mechanic took them off said they were ok. They said it needed a tune up. replaced all that. They drove said it was ok. I then drove it, it was better, didnt hear the misfire but as before when going up a hill it would do little surge or jolts like a misfire but with no sound to it. Any ideas what might be going on HELP PLEASE

 

Could it be they checked the wrong converter and might have checked if the torque converter is working correctly? Did the vehicle always have slow take-off?