FWIW, piggybacks are the king of boost control over flash. However when it comes to real timing adjustments and real fuel control, VANOs tuning, etc, flash can't be beat. With that said the BMW PID logic is a nightmare heh. In a perfect world I would only use a piggyback for boost control and doohickey gauges/meth safety and a flash for everything else.
The JB4 G5 leaves me satisfied though. And this comes from someone who's tried them all.
E90 LCI N54 6AT