The Imps completed the double over Charlton Athletic thanks to impressive strikes from Morgan Whittaker and Anthony Scully.
Michael Appleton sprung some surprises in his starting XI, with leading scorer Scully and captain Liam Bridcutt among those returning to the line-up with a change of formation to 4-3-3.
Scully was quickly involved for the Imps, creating an opening inside four minutes after good play with Jamie Robson - another player back in the starting XI - for the overlapping left-back to provide a cross for Liam Cullen who didn't have enough power on his shot to test Craig MacGillvray in the home net.
Jayden Stockley fired a snapshot wide for the hosts after seven minutes, quickly establishing himself as the main attacking threat for the Addicks.
A great pas since move down the left after 13 minutes almost brought the opener for the Imps, with cully, Cullen, Robson and Conor McGrandles involved - the move ended with Scully's pull-back looking for Whittaker being intercepted by Sean Clare.
And moments later a foul on Scully provided him with an opportunity from a free-kick just outside the area - his lofted effort looked aimed at the far top-right corner but was just too high.
Stockley will have been frustrated to see his effort come crashing back off the bar after 23 minutes, with his attempted near-post finish from a right-wing cross seemingly coming via a thigh.
Charlton's Corey Blackett-Taylor tried his luck after 24 minutes, but Liam Bridcutt was on hand to block.
The opening goal did go the way of City after 33 minutes, and again it was a well-worked move which started on the left.
The move was started by Robson, with the ball moved smartly through Cullen then Fiorini who fed the ball out to Whittaker. He initially looked to have loads of space but with two defenders quickly closing down the angle he cut inside, got past a further three Addicks men, before firing low into the bottom-right corner.
The day went from bad to worse for the home side three minutes later as Alex Gilbey was booked for a pull on Robson, the second time referee Bobby Madley had shown him the yellow card - having also pulled back McGrandles 10 minutes earlier - and earning himself an early bath.
That rocked the Londoners and City looked to capitalise, but Whittaker fired over while Brooke Norton-Cuffy's effort just before the break flashed narrowly wide.
Both sides had opportunities early in the second period, with Scully sending a free-kick just over after 51 minutes and Jordan Wright frantically keeping Stockley's header out of the net after 54 minutes.
The Imps had looked in control of the game, but were also reduced to 10 men after 56 minutes when Whittaker was shown a straight red after a late tackle on Ben Purrington.
The game by now was end-to-end and looked like it could go either way. Wright again pulled off a brilliant save after 61 minutes to tip away Stockley's powerful header from Conor Washington's cross.
Washington was beginning to look lively for the Addicks, with Norton-Cuffy doing brilliantly to stop him getting.a shot away after he collected a long ball over.
Jake Forster-Caskey headed over and Washington again saw an effort blocked, by McGrandles, after a cross from Clare.
City got the decisive second goal after 76 minutes with a move which started by Robson winning the ball down the left. He fed Scully, who cut inside and curled an effort into the top far corner for his 13th goal of the season.
That created vital breathing space for the Imps, who still had to dig deep to deal with the inevitable barrage from the Addicks.
Stockley did head home from a corner after 87 minutes to set up a nervy finish but, inspired by well over 1,000 travelling fans, City held on for three vital points.
Attendance: 10,091 (1,110 away)