Just bought an 85 300D turbo diesel. The car starts to makes a high pitch whine almost like a dog wistle when cruising at about 2400 to 2500 rpms. But if you push the gas ever so slight to flooring it it goes away. Seems to be coming from turbo area but It only does it driving. I have driven about 4 other mercedes and this is not the turbo spooling up but a high pitched low volume noise. From what I have driven it it also seems to get the worst fuel mileage of any 300D I have ever seen or rode in, maybe 18 MPG? But has all the power you want. I was gonna take the turbo off and give it a look over but none of the parts stores can get the turbo gasket and can only get the head set and want about $140.00 for that. thanks for any help.