I have a 2006 4x4 5.4L, with 60,000 miles. For a while now when I hit 50+mph the motor chugs in and out bad where my whole truck literally shakes and then it will kick back in when I accelerate through it, eventually, but at first there is a complete lack of power. It doesn't happen intially when I accelerate through, only when I get stuck in that midzone and downshifting back and forth? Not sure if it is a COP or spark plug problem or what? Please Help! Thanks!

 

Any CEL. Or codes?