The Turbo will make a "High Pitch Whistling" sound, which is normal when kicked in,"However", Not as high as a police siren and definitely not at low "RPMS"., When the "Turbo" kicks in (Boost) at high RPMs,The surge and thrust it makes from the Turbo's inter Fan wheel turns so fast that it becomes a forcible vacuum drawing in air and gases and blows it to the throttle body which become a mixture of the fuel that fire and boost the pistons to produce more combustion, and "Horse Power is increased 20% more with "High Octane Non Ethanol Gas," And only increases 15% more horse power if using 10% ethanol in gas! Now, The Turbo's Fan wheel is very "Balanced & Precise" while housed on it's bushing's and bearings, Heavy build up of Carbonized and Crystallization of burnt oil, will cause the bushings to wear, and therefore, causing the bearings also to be worn, "That leads to an out of precision alignment of the fan wheel, and or becomes binding from any and all obstruction and by not getting enough "Oil"!, This what causes "Loud Very high pitch "WHINING" or "Screeching"(not high pitch whistling normal)and or low pitch scraping, rubbing and or clanging noise from worn out bushings and bearings!> The Turbo's Fan Wheel! 2. Yes the engine will run without the Turbo Booster! You just have to Modify Exhaust, The Air Flow System, Plug off oil system, Terminate the Turbo relay and sensor, and Terminate the routing of the PVC to the Turbo, Plug off any vacuum lines to the turbo and or re route, and finally."Manipulate the Throttle Idling!, Now you have a Plain Jane 4, 6 or 8 cylinder engine, the Turbo is what it is "A BOOST THRUSTER ONLY! NOTE: You can get an overhaul kit for the turbo, However, If the Fan wheel shaft bearings are worn, The kit will not provide any bearings for that, They are factory sealed, and the only way to get it back to factory specifications, is send it to the manufacturer for a complete rebuild, but, the down fall is, the cost is pertneer as much as a new one, See if any salvage yards are in your area that may have a junked Volvo similar to your's and if it has a turbo, they are interchangeable! And or you might want to completely remove turbo for a complete clean up, to see if this might help, Remove turbo, disassemble, Use a couple of cans of Carburetor Spray & Throttle Spray, Tooth Brush, small thin wire brush with brass bristles, paper clips (steel wire) for small holes (Vacuum & etc.) can of Brake Free Spray, can of Penetrating oil, and finish up with a can of very thin oil lube spraying the parts!., Also, Spray and clean around the Fan Wheel good and lubricate good! Should help!
