The Pilgrims progressed into the Football Conference Youth Alliance League Cup second round after a 5-4 win in Suffolk.
United had twice been pegged back early on, before surging into an unassailable 5-2 lead which was cut twice late on by the hosts. Miles Lynch was United’s other scorer.
Boston (4-3-3): Jamie Bradley; Daniel Worthington (David Olalere 65), Daniel Moulds, Billy Hodgkiss, Jack McCallum (Conor Allen 50); Miles Lynch, Jack Dykes, Corey Newman; Scott Floyd, Louis Saebe, Bradley Easey (Jack Foyster 46).