The Pilgrims won 3-1 at King's Lynn Town, with Michael Clunan cutting the deficit from the penalty spot late on.
United fielded powerful Stamford AFC striker Gregg Smith, who is poised to complete a move to The Jakemans Stadium.
Boston (4-4-2): Christian Dibble; Trialist (Herve Pepe-Ngoma 46), Joe Maguire, Trialist (Joe Burgess 75), Courtney Wildin; Liam Adams (Marcus Marshall 46), Callum Chippendale, Lewis Hilliard, Jason St Juste; Lamin Colley, Gregg Smith (Waide Fairhurst 46). Sub (not used): Michael Emery (gk).
Referee: Neil Walker.
Attendance: 369.