The Pilgrims, making a rare appearance on the main pitch at the Jakemans Community Stadium, were beaten 5-2 by Stockport County.
Foster and Johnson had got the Pilgrims back into contention at half-time – but two goals in the final five minutes sealed the Hatters’ victory.
Boston (4-2-2-2): Oliver Ford; Taylor Jaine, Bailey Dilley, Owen Sheriff, Zane Millar; Mackenzie Burdass, Han Stevens; Finlay Armond, Jack Waddington; Elliot Foster, Ben Johnson. Subs (used): Krisztian Gagyi, Sam Harris, Jake Henderson, Logan Tate.
Referee: Ian Ruddock.
Attendance: 59.