Just a sidenote. Ford Racing injectors are the same as regular dealership bought injectors or any Ford injector. Venom rebuilds cores and are NOT new injectors though they charge like they are but they are balanced. The best bet is a set of ACCEL injectors which are brand new and are a balanced set which runs about $30 a piece or $280 - $290 a set.
There is an article somewhere on the net about cleaning injectors and testing them. The author states that overnight soaking really tells the truth about buildups inside the injector even after the screens/filters have been removed. The only thing I didn't understand is how he was able to submerge them and the coils didn't short out when he energized them because the two connectors just slip through the plastic outer housing. Possibly a good inner seal is involved somehow.
And finally, Ford stock injectors are of the pintle design which is more prone to buildups. I chose to go with the ACCEL units after researching all of this and also found they have a disc - design which gives a better spray pattern and is better at self cleaning. For all of these reasons, and the fact that I wanted to be sure that I didn't have any fuel flow problems, I just threw a set of these ACCEL injectors in. They seem like the best bang for the buck. Afterall, try diagnosing an injector which is a tad lean causing a misfire or periodic stumble when the engine is not up to temperature or when in the closed-loop mode of operation.