Hello, I think you ought to listen to what your mother had said? because you are not reading your information correct.All turbo Volvo`s have a built in pressure relief (set at boost 14psi) for the fuel supply so that you don`t damage the engine. If the waste gate flexible tube ruptures due to age or whatever you would have max. boost while you were driving and then it could be BANG depending on your speed etc. or severe detonation. You cannot have detonation with no fuel supply because their simply is not any fuel for the explosion. A lot of my information came from turbobricks some 4 yrs ago when the website was larger with more info. they seemed now to have condensed it somewhat. Also the Volvo models must differ from the countries as in the UK my 1991 2.0 SE Wentworth Turbo had a calibrated boost gauge which went from 0 to 20psi so one had an idea what boost you were pulling. Also you should fit a Power Boost Valve for the fuel injection. It replaces the pressure valve on the fuel rail, but it is adjustable by spanner and a screwdriver so as to set the air/fuel ratio. You buy the one for your model as it is pre adjusted to suit and depending on engine conditions it is correct one quarter of a turn either way. You can check your plug color at different speeds by stopping quick,let it cool down sufficient to remove a plug. I would rather check a plug than a gauge. You only now what the gauge tells you and not the engine. Regards