Last Saturday I replaced my #3 injector. It tested OK on my VOM but it was bad because the problem is totally gone. Sometimes you need a scope to find electrical bugs. Mine missed every so often for months. I had +4s and Magnacore wires which I replaced anyway in search of a solution. The miss started to effect the idle; that's when I finally caught it. When I pulled #3 wire from the coil pack there was no difference in the idle. So it was either the injector, the wiring, or the computer. The wiring color codes changed with the Ford retrofit, I wrote down the new ones when the manifold was off. Usually the problem is the injector since it is a moving part and gasoline deposits ruin them from the inside. Something the best filters can't remove.
