'91 200 q hesitation-btdt?

["Sherry & Chuck Clark" <clark@rmi.net>]

 Hello group,
  Well, as the header indicates, I've got a friend with this problem
in his '91 200 20v q.  He just got here from the West coast where
the problem was not present at sea level.  It's got a TAP chip and
spring. He really notices the hesitation when he slowly gets on the
boost at around 3500rpm to redline. If he's light on the throttle, it
really isn't noticeable. If he turns down the wastegate spring giving
less tension on the spring, there is less hesitation. Car has 91k mi
on it. Any 20v turbo owners btdt or have any clue to offer? Altitude
have anything to do with it? No codes by the way. Thanks for any
help possible. 

Chad Clark '87 5k Tq
Colorado Springs, CO