The Pilgrims were beaten 2-1 on the road for the fifth time this season courtesy of Curzon Ashton strikes either side of Tshimanga's 54th minute leveller.
Jordon Wright on seven minutes and Richie Baker in the 63rd minute did the damage for the home side, who climbed into a play-off place in the process.
The Pilgrims, with two debutants in their starting XI, started brightly and one of the newcomers — Peterborough United loanee Morgan Penfold — blasted wide after just two minutes.
United’s second new arrival — York City loanee Sam Muggleton — hurled in several of his trademark long throws in the early stages, but Curzon stood firm.
The Nash took the lead in the seventh minute when Joe Guest got the better of Liam Wakefield to cross from the left and WRIGHT slammed the ball home from close-range.
The match was played in blustery conditions throughout and Penfold remained at the forefront of United’s best play. He saw one effort blocked brilliantly by Steve Howson before charging down a Cameron Mason clearance and watching the ball trickle wide of the gaping net.
Ashley Hemmings was introduced at half-time and he had an immediate impact.
It was Hemmings’ shot which led to United’s equaliser nine minutes after the break. His firm drive was beaten aside by Mason but TSHIMANGA was well-positioned to rifle home the loose ball.
Shane Killock’s header was subsequently hacked off the line by Chris Rowney, from a Hemmings corner, as United sensed blood.
The Pilgrims’ hopes of a first away league win of the season were left in tatters though when Niall Cummins’ cross was met by the head of BAKER, who had ghosted into the area unmarked.
The Nash rattled a post through Wright moments later but the remainder of the match passed without noteworthy goalscoring chances and United were left to contemplate yet more frustration on the road.
Curzon (3-5-2): Cameron Mason; Danny Shaw, Steve Howson, Matt Regan; Chris Rowney, Jordon Wright (Luke Clark 74), Richie Baker, Paul Marshall (Matt Crothers 79), Joe Guest; Ben Wharton (Tyrell McKenzie 84), Niall Cummins. Subs (not used): Max Leonard, Oliver Thornley.
Boston (3-5-2): George Willis; Liam Wakefield, Shane Killock, Brad McGowan; James Clifton (Karl Hawley 73), Jack Thomas, Jamie McGuire (Ashley Hemmings 46), Jordan Keane, Sam Muggleton; Kabongo Tshimanga, Morgan Penfold (Jay Rollins 83). Subs (not used): Adam Chapman, Gregg Smith.
Referee: John Matthews.