Here's my take...de-tuning the car is not a good idea for a few reasons. One is that however you achieve the lower level of performance you're going to alter the way the car accelerates in bad way. This could be dangerous if the car is too sluggish on the highway or stalls when pulling through an intersection. If you turn down the boost things like this could happen because the compression ratio is so low. I really have to ask though, why? I can't even begin to imagine how many variants of turbocharged Volvos are on the road. I have yet to hear of an epidemic of Volvo drivers not being able to help getting speeding tickets. In stock form (especially with over 100K) they really aren't that fast. They do have some pep to them and of course you can get a speeding ticket in anything, but still-it's a 3000+lb car with 160 HP. My upcoming turbo buildup should hit about 215 HP at the flywheel-still no serious street machine.

Later,

Matthew