...And how popular is FM piracy in NYC?
popular enough that for every commercial NYC FM station, there are 5 pirate NYC FM stations.
there are so many NYC FM pirates that there is competition between them, many of them transmit on top of each other in an effort to "block out" the other pirate, there are sometimes physical altercations between them over the little space available on the FM dial and who has the cheaper offer for advertisements and commercials.
however, it is extremely rare to find an FM pirate in NYC that is operating their equipment inside specifications that does not cause 1/2 power or more of the 2nd harmonics generated, deviation that exceeds 150Khz and generally sounding terrible overall with massive azimuth errors and background noise.
add to this that more than most of them are broadcasts that are directed at the large ethnic population (mostly in Brooklyn).
out of this huge mess of garbage, its very very unlikely that there is a "hobby" NYC FM pirate.
its not longer what it used to be years ago.