How well have you been doing your maintenance on the truck and how much mileage?
The first thing I would do is remove the throttlebody and check for carbon deposits on the back side of it.
This is an easy job which anyone can do.
If it is dirty clean and reinstall.
I would also make sure the sparkplugs are good.
The early F-150,250 had problems breaking spark plugs when removing them.
The switch was made in the middle of the 2008 model year.
To check which model you have remove 1 of the COP's (Coil On Plug) by removing the small 3mm screw (7mm head) holding the COP to the valve cover and gently pull out the COP. (clean dirt and debris from around the COP before removal).
If the rubber boot is brown like this one you are lucky and they are the new style plugs and can be easily replaced.
If the boot is black then the sparkplug job becomes much more difficult because the plugs can break easily if they are originals or if anti seize was not used on the shields when they were installed. I have the removal tool if needed.
There can be 3 different problems and you may get away with a cheap fix.
The first thing to understand is how the system works.
VCT= Variable Cam Timing
VCT is run off of engine oil pressure. When the engine is cold the oil pressure is much higher than when the oil is hot.
The first question is if the problem exists when the truck is both hot and cold?
If it only happens when hot then I would suspect an oil problem.
Oil pressure should be 75 PSI at 2,000 RPM (Engine at normal operating temperature.)
This means run the engine till the radiator fan comes on at least once .
Do you use genuine Ford filters, good quality oil, good oil change intervals, drive the truck at least 20 minutes every trip because you can't burn off water vapor and contaminants in short trips.
The problem is oil pressure, to get to the oil pump the front cover and timing chains need to be removed.
If you're going this far you should change the timing components at the same time.
The oil pump can be purchased through Ford Racing for as low as $80.00US.
The Timing kit will cost you about $630.00 US for the complete kit (do the complete kit)
The 3rd thing can be the VCT solenoids.
You can find the VCT solenoids 8L3Z-6M280-B for as low as $44.63 each X (2).
You can do the VCT solenoids yourself if you are handy. There are YouTube videos showing this.
If it is oil pressure related I would do an oil change with a good engine flush prior to the change.
I would go with 1 grade thicker oil than the 5W-20 factory fill and see if it helps. I would go with 10W-30 once the weather gets better.
Engine oil pressure is critical in these engines, use only OEM ford or Ford Racing parts. Ford Racing can sometimes be found for cheaper than Ford parts and they are exactly the same.
Call Sylvain at Billet Pro Shop if you want to know what it would cost to fix. 1(450) 245-7007
He is located in Napi across the street from the track. He does Ford modular work all day long.
What did the dealer quote you? What parts did they want to replace?