I purchased my 2006 at an auction last month.It has 44,xxx miles.It is out of warranty as it had a 3/36 warranty.Ford put a left cat on it (it was plugged) at 40,xxx miles.When I bought the truck the left cat was plugged/melted so the motor killed the new left cat in 4,000 miles.I replaced the cat myself.Ford refused to do it again under the emission warranty because obviously the dealer that changed it 4,000 miles ago did'nt properly identify the problem that killed the cat.I tested the right cat and retested the left side exhaust after the new cat was installed and had zero back pressure on either side with a warm engine.This truck runs great with lots of power before it is totally warmed up.As the engine is run for a longer time,it starts to lose power and run rough.It will also stall at stops.There is a little mechanical noise in the top end also.I am running 5w20 synthetic blend and a motorcraft 820s filter.If I restart the engine after it stalls it acts like the timing is way off and will kick back against the starter but will start.Once running it will idle but will have a very loud clatter coming from the area of the phasers on both sides of the motor.It will also spit out misfire codes,cam sensor codes and lean codes.I had the valve cover off and this engine is cleaner than you can believe.I am thinking that when the engine is fully warmed up that the oil pressure to the top end is somehow restricted or inadequate so that the tensioners and phasers are freaking out causing wicked valve timing variations.The scanner shows some pretty high cam sensor error readings for both sides which increase with RPM,s.If I tap in a pressure guage at the sensor location what would be an acceptable reading?I know that the factory guage is useless as it is fed info from a snap switch and not a true sensor. If I end up tearing this engine apart due to suspected oil passage restriction /plugging how successful would I be to properly determing the exact problem?I don't mind spending a lot of time to do this as I know that a 2,000 dollar+ used engine might not be any better.I am an ASE master tech with 30 years experience and am not afraid to dive into this.There are a lot of Ford trucks around with this engine so I figure that the first one I do is "5.4 college education".Thanks in advance for any help you folks can offer.

 

Thumper, go to this link. You might find it interesting.
https://www.ford-trucks.com/forums/8...ters-only.html