I've experienced the same thing. Most often in 3rd gear around 5K RPM
(I have a manual transmission in my T5). I think the ECU is adjusting
boost to prevent pinging. I do not notice it all the time (seems to be
related to air temperature, fuel I've purchased, etc.). My
turbo is a 98 and the 98's ECU does allow a bit more boost and has more
"controls" to back it off then earlier ECUs (newer ECUs are a bit more
sophisticated) so maybe I'm just noticing it more with my 98. But I
definitely can feel the power surge a bit at times.

You could try resetting the ECU back to default settings. It then
re-learns based on fuel, etc. When I do this my car is noticeably
faster for a short period (then I guess it tunes back to the 91 octane
we have for premium here in CA). To do this, disconnect the battery
over night. When reconnected you will have to plug in the radio code,
reset the clock and reset the radio pre-sets. Probably won't make any
real difference but it is interesting to "feel" how fast my car is
for a short time after doing this.