First check boost leaks.
Secondly I'm going to say you have a stock dump pipe with Both Cat's in place.
TBH this annoyed me alot when I first bought the MPS.
Even after few mods and tune was sill there, but going from an NA you notice it alot more.
Then I did dump pipe and in the process changed both cats to a single 200Cel unit.
issue totally gone
(well to a point... its still a turbo car).
The stock dump is a very poor design with crap flow and large bottle neck with a lot of turbulence.
then you have 2 very restrictive cats just a few inches down from the turbo making things worse.
Im going to say Normal from your description, and you notice it heaps because you are use to NA.
Time for MODS!
But i always encourage Boost leak tests!