Your ECU definitely needs to be tuned in order to take full advantage of the meth injection
Here’s a common kit used amongst bmws
https://www.ecstuning.com/b-aem-elec...n-kit/30-3000/
From my understanding meth injection works via throwing in more cool air and decreasing combustion temperatures which results in more power.
The kit comes with a controller that lets you set at what rpm and boost should the injection happen.
Here’s a link explaining what it is and how it works
https://youtu.be/HkPFZWd8wj4