I ran a boost controller with a stock ECU, so I dont agree that you can't run more boost. I ran 14. There is no fuel cut to speak of on my car, it would run so rich I would have misfire on the top end though.
However, its freaking pointless, my car ran SO rich under boost that it was not making jack for power. I swapped to an apexi power FC, and on its base maps it ran much better. Idle was 100% tamer as well.
You have to run some sort of management, stony is so right. You leave so much power/driveability/economy on the table with stock EFI.
Evan