This, exactly. I'm open to the idea of a tune accounting for WMI, but I'd need to have a fallback in case I run out or something goes wrong with the WMI setup. Short of keeping flashing equipment in the car, I'm not sure what the options are for on-the-go retuning. Part of the reason I was interested in the EK1.As in the JB4 is adjusting what the ECU is seeing. If something goes wrong or you simply turn it back to map 0, the ecu is back to doing all of the work. This is what I mean by "outside of the tune". The factory closed loop maps are unchanged. The JB4 is fooling the sensors into reading something else in order to find optimizations in performance.
On the topic of wmi. I'm not referring to the car being lean. The car could have plenty of fuel and correct AFR, but not enough knock protection (ie. octane, or more specifically AKI) for a given timing or boost increase. Which your wideband isn't going to tell you.
So meth outside the tune = so long as you're running the correct gas you're supposed to be running, you're fine.
meth in the tune = you need to be running meth to avoid knock with the demands of the tune.
the difference between ecu vs piggyback is that, if your jb4 is handling everything, if you run out of meth, the jb4 will just dial it back. Whereas best case scenario, the ECU will see knock and pull timing. worst case scenario, boom.