I have a couple of books (in French) on the history of Coteau-du-Lac.Author is Hector Besner, both titled "Histoire de Coteau-du-Lac.Vol 1 is general history and Vol 2 is more about the religious history.
At a glance, found a couple of mentions of Poirier, roughly translated:
Vol 1, page 80 Concessions south of the Délisle River.Lots 3 acres across by 20 acres deep. #3, Jos. Poirier, notary named "Gabrion", date 10 July 1789.
Vol 2, page 432 List of Parishioners of Saint-Ignace de Soulanges from 1830 to 1833 Poirier, Jean-Baptiste
Vol 2, page 445 List of Churchwardens from 1833 to 1997 Poirier, Albert - 1945-46-47