Ashton Taylor's second half goal was nothing more than a consolation as Lee Mitchell's side found Kidderminster Harriers too hot to handle at COSE, with five of their own first choice players missing.
The Pilgrims were beaten 5-1, having trailed 3-0 at half-time before Taylor's fine strike.
Boston (4-2-3-1): Jake Frestle; James Mallender (Arron Bailey 70), Harry Cranfield, Kai Skinner, Jamie Gaukroger; Joe Hardstaff, Ashton Taylor; Henry Beedham (Finlay Armond 55), Will Jackson, Ben Johnson (Tom Wilkinson 65); Jack Bastow.