If yours is/was an LPT originally, it won't have the boost gauge as far as i understand things.
The MAF takes the place of a MAP sensor usually, the MAP tends to eliminate the need for a MAF as the same info can be calculated by the ECU from engine speed, throttle position (through a throttle potentiometer, rather than just two switches as on the majority of the Volvo systems) and Manifold Absolute Pressure.
