smooth idle,but rough when hard acceleration

[hoisingtons]

i have a 98 expedition...i have changed out #4 coil pack,#3 boot and spring...it runs great if you accelerate normal,but if you do any hard acceleration...its rough and the CEL flashes,but does not stay on....i have checked the elbow,no cracks,have also cleaned throttle body as well and ran a can of seafoam through it.....any suggestions for next step...

 

[hwy73]

I would..........Check for stored codes
Fuel filter been changed recently?
Make sure intake tube between MAF and Throttle Body is tight/no leaks
Another COP could be on the way out
Needs Plugs

 

[BANGEREXPO76]

I would definately change the plugs as well as pull codes.