Any chance the white puff of smoke may be from a partial compressor stall? Power was low then bumping it up a bit rather then raising it slowly. If you watch the video you can hear a slight pop as the smoke puffs out.
Not noticed in the cabin though.
I found this youtube video of a BK117 helicopters engine doing something similar.
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https://www.youtube.com/watch?v=H7DIAnz40dc]