New to form and looking for help.

I have a 06 F250 with a 5.4L truck has 50k on it. I have been reading many articles on the issues with can phaser/cam tensions/cam chain issues. I have noticed that when I start the truck a get a knocking noise that goes away with in 5 sec of the truck starting. I have been noticing lateley if I am sitting still at a light and go to give it gas for a short period I get a sound that sounds like a cam chain slap for a split second as the truck starts to move it goes away. I had a friend of mine stand outside the truck and put in gear and power brake it and as it decealarates you hear a quick cam chain slap. I use Catrol 5-20w standard oil and motor craft oil filter. Any suggestions would be apppreciated. I purchased the truck with #6k on it 3 years ago I have replaced the leaking exhaust manifold with Gibson stainless unit and have confirmed they are not leaking again. I have heard that the hydrolic cam tensioners sometimes get clogged and people have run a oil additive to clean out clog. Any suggestions/help would be very much appreciated.

 

A knocking noise that goes away within 5 seconds of starting the truck is probably piston slap, not a cam phaser.