Your missing something here Melv.

And its this:
When the map reaches 4.9Volts it still has rpm factors etc it can read to keep rpm based fuelling correct for rpm. And we can still increase the values and duration it oputs out at that level, but we cannot change the fact it is no longer scalable against pressure.

Put another way:
What it can NOT do is be correct at 2bar of boost(4.9v) and 2.5bar (4.9v) and 3bar of boost (4.9v)

What has to be done is map at perfectly at 3bar of boost, then anything below this will simply be a bit rich

Another good reason why folks shouldnt go the other way either

Tuner: "Set the boost at 34psi"

Customer "So i set it at 26psi for safety"... "Damn, the rings picked up "

The moral? "Always do what your tuner told you to do.." roflol