its not a problem, its just how the turbo works. mazda picked a turbo that would give you that instant power feeling which this one does. i dont think its that hard to stay out of boost. drop down a gear if you do, you probably get it to build more because you are in a high gear with low rpm's so the extra load will spool the turbo faster.
Boost isn't RPM related. Boost is throttle percentage related.
You mash pedal, turbo spools.