Oh and by the way. When they finally agree that the head gaskets are toast, find a machine shop local to you that can mill heads. You DO NOT want the Ford dealer checking the heads. Their procedure is not sufficient enough to determine this.
It may cost you some cash, but trust me, it will be well worth whatever you have to pay to get this done. If it is not done, and the heads are not flat/straight enough, another head gasket failure could be in your future.
Have the machine shop check the heads for flat/straight and have them magnafluxed for cracking, especially in the exhaust valve seat area.
When the machine shop goes to mill the heads, tell them that they can not machine off more than .07 to achieve flat. If they must, you have to buy a new head.
Then, buy a set of ARP head studs. DO NOT use the stock FORD head bolts. BIG difference.
The stock bolts are of the "Torque To Yield" type, which means that the bolts are designed to stretch to a certain point to maintain clamping force. Not the best design for a high compression engine. They are sufficient for what the stock version (the International VT365) of this engine is, but FORD changed the programming in the PCM to gain "best in class" status with horsepower and torque. Not a big deal, but a small contributing factor. The studs are a MUCH better choice.
The ARP head studs do not stretch. The nuts on top of the studs maintains the clamping force.
ARP Head studs for $400
This is definitely one of those jobs where, even though you have a warranty, if you spend some of your cash to get better parts/machining, you will be VERY glad that you did in the end.