I have a 2005 F350 with the Triton V10 the motor has been rebuilt and had to replace all coil packs at startup runs just fine as I build up speed roughly 45 mph it starts to pop the backfire if I give it any throttle it does not get any faster just makes it worse any ideas as what I can do? I had to replace some of the ends plugs off the wire harness and that helped it some. It was a lot worse before I replaced the ends

 

Is it popping in the intake manifold ?

If so check the valve timing. Or the condition of intake valves, compression or cylinder leak down test.

 

It sounds like it's popping through the intake.
I've ran a compression test and everything's good there.
I just replaced all the coil packs.
It only happens when I get up in RPMs .
At about 45 to 55 mph

 

Is there any way you might be able to post the fuel trim info?
IF,,,,,,,, it is a lean misfire opening the throttle adding more air will make it worse.