The Pilgrims were heading to a fifth consecutive National League North reversal until Pollock stepped up from the spot to level and deny Gloucester City all three points.
Debutant Billy Chadwick had spectacularly fired United into the lead - but the Pilgrims trailed at half-time following Gloucester replies through Dominic McHale and Tope Obadeyi.
Chadwick was named in the United starting XI, with fellow newcomer Luther Munakandafa on the bench. Zak Mills was deemed only fit enough for a substitute's role due to illness.
The match started in monsoon-like conditions - but the sun was shining by the time United took a 23rd minute lead. CHADWICK broke from his own half, exchanged passes with Tre Mitford, before advancing and beating Brandon Hall from 20 yards with a brilliant finish.
The visitors levelled a dozen minutes later when Matt McClure charged down Sam Long's attempted clearance - and Ben Pollock inadvertently poked the loose ball into the path of McHALE to finish from 18 yards into an unguarded net.
Gloucester went ahead in first half stoppage time when Tommy O'Sullivan kept a loose ball alive and OBADEYI swept home from close-range.
City's Hall made a fine double save after the break to deny Chadwick and then Scott Pollock - and despite plenty of endeavour, it appeared United would taste defeat once again.
But referee Ben Tomlinson awarded Jake Wright a generous penalty for a tangle with Daniel Leadbitter - and Scott POLLOCK did the rest from the 12-yard mark.
Boston (4-1-2-1-2): Sam Long; Keenan Ferguson, Luke Shiels (Jo Cummings 58), Ben Pollock, Harry Lewis; Tom Platt; Scott Pollock, Sam McLintock (Luther Munakandafa 68); Billy Chadwick; Jordan Burrow, Tre Mitford (Jake Wright 77). Subs (not used): Will Atkinson, Zak Mills.
Gloucester (3-4-2-1): Brandon Hall; Daniel Leadbitter, Ben Morgan, Ben Nugent, Jack James, Jacob Berkeley-Agyepong (Matthew Barnes-Homer 83), Owen Evans, Junior Tiensia; Dominic McHale (Jake Andrews 78), Tope Obadeyi; Matt McClure (Tommy O'Sullivan 40). Subs (not used): Jack Hill, Billy Johnson (gk).
Referee: Ben Tomlinson.
Attendance: 1,316 (15 visitors).
PIC: Russell Dossett.