The ECM fires the injectors sequentially, (no two fire at the same time). If he said they were all pulsing correctly, chances are it's not the ECM. Make sure you can return it if that doesn't fix the problem. (This is the importance of proper diagnosis)
Did you do the first two steps? They make sure the plugs and the wires are good. Swapping #1 & #4 plug wires, and the miss stays on #1, the injector is not firing, BUT, you need to know the plug and wire are ok. If the plug or the wire is faulty on cylinder #1, the miss will stay on cylinder #1. After each of the tests I mentioned in the previous post, you need to re-set the OBDII and drive it until the SES light comes on. The ECM will tell you what cylinder is missing.