You would have to get Ford or Ford-level equipment to test the injectors directly, very expensive on your own. An indirect way is the balance test, and ignition waveform. Basically, we want to prove that the problem exists in the engine and not outside or vice versa. If the balance test fails at high rpm, then you can look at the graphs to identify the miscreant cylinder(s).
A sticking injector might be an issue, given that flooring from a dig outputs a fuel smell. How intense was it? WOT IS going to run richer, so a mild smell would be expected because you cannot make that smooth transition at the drop of a dime. There's always a small window of inefficiency. So how bad the smell is will tell you whether that is indeed an issue to be researched.
Now, looking back, you have a new engine in there right? Long block new injectors new everything except manifolds?
