The following diagram provides a high-level view of how to wire in a second bank of injectors for use with ECMLink's secondary fuel control feature. This diagram illustrates 4 primary injectors and 4 secondary injectors. But, really, there's no reason you couldn't run 4 and 6 or whatever else. You just have to calculate the primary and secondary global fuel adjustments accordingly.

The “driver box” in this example would be any standard peak/hold injector driver box. Typical examples include the AEM driver box, but there are several others as well in varying price ranges. There is one that's used by the mega-squirt guys pretty regularly that's fairly inexpensive, especially if you're willing (and able!) to do your own quality solder work.

You'll notice that the stock injector resistor pack is missing from the diagram. That's on purpose. You don't use it. The peak/hold drivers provided by the driver box simply don't need the inline resistors.