Help! !997 Expedition problems.

[wingman5521]

I have a 1997 Ford Expedition 5.4L when I hold the truck at a steady 40 or 50the truck hesitates and rocks a little and when I does I have no horsepower. I replaced the fuel filter, changed the plugs, serviced the injectors and fuel system, replaced the IAC valve, replaced the ERG valve and O2 sensors running out of ideas. Also when stopped if I press the gas and turn theres a vibration I checked and serviced the rear but all is well.
I have K&N cold air intake, Gidson shorter headers, Edge evolution programmer. Any one with ideas please HELP. No check engine codes.

 

[EXP Edition]

I have the same exact problem. I haven't further diagnosed it, but my main guess is a leaky intake manifold gasket or a vacuum leak.

 

[ChuckD]

Torque Converter shudder. When was the last time you serviced your tranny?

 

[wingman5521]

Shudder?

My tranny was serviced last year what is the fix for torque convertor shudder I was told recently that could be the problem and what are the other signs of that problem.

 

[KWT2000]

how long have you had the problem?? are you sure when it was serviced they used the correct fluid?? i have seen shops use regular dexron/mercon and have this problem come up. also some shops use dexron/mercon then they add the additive bottle for ford or chrysler they say the 10 ounze bottle is enough but i cant belive it