The ECU picks up the change in wastegate control rod operation, and adjusts (retards) engine performance accordingly. This is well-documented, and you can read more about it in the q+a at http://www.tme.com. The chip is the best way to get imcreased performance (you also ordered the free-flow exhaust, including the 3" downpipe, too, didn't you?).

A manual boost controller is another possibility - it bypasses the ECU and there's one available for pocket change by Dawes. But be careful. Dial up too much boost and you'll be fishing pistons out of the oil pan. (Volvo mated the ECU to the turbo for a reason.)

The times are indeed slow, and the altitude may also be part of the story. Have you inquired as to whether there's a high-altitude program for the ECU?