Ford Repair: 2006 hesitation problem, hesitation problem, unfortunatley

Question
QUESTION: After 2 tries and $460 at a Ford dealership my 2006 Expedition still has the same problem. I accelerate to 45mph and 2000rpm the transmission shifts to a higher gear and the rpm drops to 1200 rpm. When I accelerate again I get short hesitations until I push down harder on the gas pedal and the engine rpms go back to 2000rpm. The Ford mechanic changed and flushed the transmission fluid the 1st time and it didn't help. The 2nd time they found number 6 spark plug and coil to be faulty. Well, it still has the same problem. Any idea ?

ANSWER: how many miles on this vehicle ?

---------- FOLLOW-UP ----------

QUESTION: 76,000 miles

Answer
Has your check engine light come on at all ??? apparently the are missing and engine skip.
The unfortunate part is, with out the right diag equiptment- this is gonna be a tough one for a do-it-yourselfer. My advice would have been to change all the plugs. in your vehicle's year, ford used spark plugs labeled PZ1's. They were know for breaking and causing various concerns. By changing only the one plug is they are now mis-matched to the updated plugs which i'm sure he installed the update in yours. Not saying you may not still have a coil breaking down. Unfortunatley, without a check engine light it's tough to tell you what cylinder i doing it. bring it back to the dealer, they have a computer they can install on your car that you will actually leave the dealership with called a flight recorder. when the problem happens, you push a button and it will record what the computer see's. then you bring it back to the dealer and they can see what is happening