OK so I have a 2005 ford fx4 with the 5.4. It has 155000 miles on truck I replaced the motor as I purchased a crate long block and it now has 2000 miles on it. Every since day one it has fell on it face under acceleration and Cruise control is a joke because it struggles to maintain with the fresh motor I did a fresh tune

Changed plugs and cop's
Cleaned the mass air and throttle body
Reflashed the computer (well ford did)
I have changed me vct solinoids
Air and fuel filter
Getting my cats tested in the morning

So this problem is hard to describe I can drive the truck and do but o have to baby the throttle to keep it form just falling on its face but sometimes I get in it and it runs good and strong and others not so I can't rule it to be once it heats up
In town and on dirt road 90% of the time it runs fine it upper end hyw that gets it
I have found that it will maintain ((for the most part on the hyw)) of i draft a 18 wheeler and turn the ac off.
Now this truck is my baby and I wanna keep it but I need help in my not inconsiderable experience I am stumped

PS I have also done the sea form through brake booster ever tho its a new engine
In my opinion it loading up the engine somehow some way pcv maybe cause oil pan leaks and it seam more when its really struggles

 

Seriously nobody
Thought I might add I tested the cats and have none and I'm replacing the fuel pump

 

If you used aftermarket coils, this could be your problem. I did the same thing. Used accel coils, truck ran rough. New coils but still didn't work right. Switched to motorcraft coils and the problems went away. This does not throw engine codes either. I had to get the truck professionally scanned. I was missing on three cylinders. The accel coils had spark, but they just didn't work right. Hope this helps