140 must be in those silly metric Canadian units, eh?
I get a whistle when the windows are open even at more (ahem) "reasonable" speeds. It comes from the molding on the back of the back door windows (between the rolldown and the fixed triangle glass). I'm going to slightly trim the upper rubber (I think) to smooth the airflow.
100MPH will get you some other noises too - agreed with the above to check turbo whistle. If you want to see if it's the windshield molding, use some duct (oops, scratch that) "racing" tape to cover offending parts of the molding, or wipers, or whatever. When the whistle stops you've found your source. And if you want to KEEP it there, you can even get colored racers tape... check Summit Racing... I think they even have Orange...