I had a very similar issue with my 06 Gallardo. It was described as an "intake whistle". At the 7500 mile service my dealer investigated the problem. From what I recall him saying, they found that the gasket between the throttle body and the intake plenum was slightly missaligned and interferring with the airflow through the throttle body. They trimmed away the excess. Now about 80% of the whistle is gone. I can still hear a little bit of the whistle when I get deeper into the throttle, but the annoying screech at partial throttle is gone.