Warranty isn't a selling point just a difference to consider before you take the plunge on flashing as you can't go back after:
https://f80.bimmerpost.com/forums/sh....php?t=1739110
In terms of JB4 potential if properly setup you can make pretty good power, this is a dyno of our Z4 running JB4, exhaust, 40% E85 fuel. Almost 500whp. That said there are things you can only do by adding in a flash map like exhaust burbles, speed limiter, and a few others.
