2006 5.4 with 108k on the clock. Started missing occasional so I had the plugs changed (used mc sp515 and new boots). Runs worse now with 0ccassional stuttering while in od at 1700-2200 rpm and is much worse and truck shakes really bad where before it was just a hiccup. Not throwing code but cel flashes. Did finally get my programmer to pull a p0304 code so I checked that plug all is well and changed coil pack. Drove it and it's still doing it. Should I change the rest of the coil packs or is there something else? Truck accelerates and runs good except for that. Thanks in advance!

 

I would say go back and torque all the plugs to about 20 ft/lbs and then replace all the coils then reset the pcm so the vehicle can go through the relearn process.

 

One other thing is when it does this just before the shaking begins the valves rattle a little. If I back off or accelerate it goes away

 

I am betting that plug is cracked on the porcelain. Pull it an switch it with another plug to see if the code follows.

 

Faulty/loose plugs sound like definite possibilities. Another possibility could be the connections to the coils and/or wiring.

 

I will check the plugs and connections as soon as I can (next few nights hopefully when I get time). I will pull the #4 plug and check it out as well.

 

I had similar problem on number one changed cop plug out . Cleaning old one didn't help .
Also I think putting never seize on threads can interfere with the plug torque and the primary high voltage path to the head . Thereby causing spark problems .
I had changed out the plug again, the cop and the injector first .
The cop signal to the coil is very low voltage .

 

Changed cop's no help still getting 0304. 4 plug didn't want to budge. Finally got the plug to break loose (replaced 2 weeks ago, maybe 250 miles on them) it spins freely but won't come out? What the hell is going on with it? I'm about ready to give this pos away!!!

 

I'm willing to bet that the cylinder 4 plug was not replaced. That's a hard one to get to. These plugs have a tendency to get stuck in the head and break when they are in there for a while. It's a faulty design, and why it costs so much to have them done at a shop.
I would take the truck back to wherever you had the plugs changed. Make them take that plug out with you there. No matter how much these two piece plugs suck, they won't break after 2 weeks and a few hundred miles.

 

Sounds like whoever installed it over torqued it and broke it.