The truth is, a BOV is not a good idea on the Volvo running the stock integrated engine management program. Why? Because all air taken in passes through the MAF sensor. And if you release boosted air like that, that air is NOT measured, and the ingested air will not equal the amount of air that actually reaches the comsbustion chamber.

So unless you are running an aftermarket engine management system, it's not a really good idea.

Is the sound of the BOV going off worth an increased risk of check engine lights, running rich often, therefore decreasing the life of your O2 sensors, and catalytic convertor really worth it? Not for me. Don't get me wrong, I like that sound too, but there are things you have to give up to get that sound.