Unfortunately there are many things that can cause code 1222. Here are a few things I have found over the years that have solved this code:
Have your valves adjusted if you hear alot of tapping at around 2500.
Check your intake boot for tears even small tears can open under load and will throw 1222.
Fuel pressure regulator, if it's off by 5 psi it can throw a 1222.
If your fuel injectors are very old and have a poor spray pattern can cause this code. I advise the late ford 5.0L HO or early 4.6L 4 pintle injectors. (the yellow ones)
If you car has a performance chip, take it out and see if it the code pops up.
Do a compression test, you should have no more than 20 psi deviation between each cyl.
Check your temp sensor. Also make sure you have the correct coolant temp sensor, there are two types: Blue and white. They will function if switched, however they are off by about 1000-1200 ohms cold 150-200 warm and 50-100 hot just enough to F with the DME and cause all kinds of weird and wondrous crap. The white should be used in the ETA powered cars 88 and older, the blue in 88 and up.
Don't rely on the auto parts place to give you the correct one, if you start spouting words like "ohms" or "I need the correct part" you'll scare those poor people.
And after you do any repairs, unplug the DME or disconnect the battery for 30 sec, longer if you have an air bag (the capacitor will take at least a 4-5 min to drain)