Seems that after having my turbo removed, checked for endfloat/wear. the recon place i used inform me that it has a very small amount of wear, nothing to make it siren/whistle as loud as it was. So i decided to have it cleaned, a new shaft and bearings as it was off and im intending on keeping the car. So this siren noise is still there. Its sometimes worse than others, no limp mode no over boost. In the car whilst driving, there is a high pitched hissing noise, and the wurring sound as its revved. Next is to have the boost pipework pressure tested. And replace all O-rings regardless. I suggest anyone else who has the siren noise to pressure test etc as like mine, it might be a worn seal, or as this system holds the oil, which corrodes and perrishes the rubber boost pipes, and seals, check or have them checked before you stress over needing a new/recon turbo.