If you have a bad boost leak, dirty ass filter, or map sensor isn't reading right you may not be hitting the desired boost # your tuner is calling for in the tune. Therefore the ecm will call for more vane position to try to meet that desired number. When that happens drive pressures go through the roof and there is a lot of power left on the table. Once you hit the desired number the vanes should start to open up because then the fuel won't need the help of the vanes to maintain the boost # the tune is calling for.