Laskern, in yeshivot they say that a goy whistles. A Jew does not whistle. There is, in fact, a counter-story. Somebody went to the rav after Shacharit on Rosh Chodesh and told him of the fantastic spiritual experience he had. the rav asked if he said “Yaaleh v’Yavo”. He replied that he had not and the rav told him that he had to daven again as he was not yotzeh.
