97 850 screaming schrill

I've purchased a 97 850 automatic with 114k, through a mechanic who I feel was trustworthy and knowledgeable. He was selling it for a client and did the maintenance on the car since new. He put a new air pump on the car from Volvo prior to the sale, but said it was "screaming". So before I took possession he replaced it again with another one from Volvo, but with the same result. I do not know if he changed the relay or the SAS valve, but there is a shrill coming from the front of the car. When I say a shrill I mean I can hear the noise from 50 to 70 feet away. It seams to come from center, to just off to the passenger side on the front of the engine. It goes away under load, but is fairly constant at idle wether in neutral or drive.