Not sure what the source of your info is, but - no such thing as a free lunch. Spark advance is akin to 'leading' a duck with a shotgun... the faster the duck flies, the more you have to shoot ahead of it in order to hit it. Spark advance is similar, but it is automatically controlled in your model Volvo. Advancing the spark timing may help in a certain narrow rpm range, but what you gain there you will lose in a different rev range.

The best thing to do is to make sure all ignition components are up to snuff - plugs, wires, cap and rotor. Drive wih a light foot. Want more scoot? Put in a performance cam and a port exhaust.