Before we had engine management, it seems MBC's would cause mid-throttle/full boost elevated EGT's. On race day, people were known to use MBC's to up the boost since, it was said, they weren't as bad for the motor at WOT. But even at full throttle, many a MBC would hold full boost to redline, pushing the turbo dangerously outside it's efficiency range. Grown men cried.
Today we have much more betterer MBC's available (like the Hallman Pro RX that I run) and engine management.
And you don't necessarily need to be tuned for the MBC but you do need to be tuned. I wouldn't have run one if my tuner hadn't recommended it. And having an EGT gauge makes me much more comfortable running it too.
Anybody who doubts the benefits didn't drive my car before and after. The car feels much torquier and boost response is night and day. Honestly, AutoX is where it really shines. 1st and 2nd gears build boost faster with the MBC.
As for the danger of removing the ECU's boost control, thankfully, the ECU can still cut power when you reach a boost threshold that your tuner can set.
AWD Launch, read Ed's (EQ Tuning) posts in
this thread. Good info right thar.