I wouldn't get the S-afc. It modifies the fuel by manipulating the air meter signal. Our ECU's will try to tune around it. I've got an e-manage and will be putting it in the car. It appears to be a much more flexible unit and allows you to fine tune on a 16 by 16 map for both fuel and ignition. Also, it takes throttle opening into account so you can set your fuel enrichment to a specific throttle opening point. That way we can tune around the factory ECU going into open loop at WOT and running rich. Just pull a bit of fuel out of it when it goes into open loop. I just need to find out the throttle percentage where the ECU goes into open loop.
It controls the injectors two ways. If you use the included harness it modifies the air meter signal much like the S-afc and only allows you to modify the fuel at 5 set points. 2K, 3K, 4K, 5K and 6K RPM. It interpolates your settings between points, and uses the 2K setting for RPM points below 2K, and the 6K setting for points over 6K. Not the greatest control.
If you get the optional injector harness and software then it adjusts the actual signal to the injectors to control duty cycle. This is a much better way to control things. The factory ECU does a good job of keeping a/f ratios right at 14.7. All we really need to adjust are some slightly richer 60-80% part throttle settings (for power) and then trim some fuel out of it when it goes to open loop.
The optional ignition harness allows you to adjust extra advance or retard based on the factory ECU's setting. This is one of the main reasons I purchased this unit as the stock ECU on my ES model has a really slow advance curve.
The neat thing about the e-manage is that it also controls additional injectors and can retard timing under boost as well as index additional injection under boost. It's just a lot more unit for the money.
I'm still working on getting the right settings for it internally (there are 3 rotary switches that need to be set for the type of engine and MAF/MAP system) but once I do I've already figured out the factory ECU wiring for which wires control what.
