Holloway's future has been in doubt and it looked bleak for him when David Friio put Plymouth ahead after just seven minutes.
QPR had struggled to defend set-pieces this season and were caught out again when Friio headed Paul Wotton's inswinging corner past keeper Chris Day.
Rangers almost equalised when Kevin Gallen controlled Martin Rowlands' cross and laid the ball off to Furlong to fire just wide of the target.
The home side continued to press and again came close to scoring when Lee Cook latched on to Gallen's clever pass and sent a right-foot shot wide.
But Furlong made no mistake in the 26th minute.
Rowlands' looping cross looked to be no real threat to Argyle, but Cook rose at the far post to head the ball into the path of Furlong and he smashed in his second goal of the season.
Worse almost followed for Plymouth when Rowlands curled a 25-yard free-kick just wide, although Argyle rallied late in the first half and Day did well to hold Micky Evans' header.
The visitors stepped up a gear after the break but were unable to make the most of mistakes by Marc Bircham and Georges Santos.
First Bircham's misplaced pass put David Norris through on goal but he steered wide of the goal with just Day to beat. Stevie Crawford then failed to capitalise after Santos clumsily failed to cut out Norris' low cross.
Holloway made a double substitution on the hour mark to try and galvanise his side. Rowlands and Cook were replaced by Jamie Cureton and Kevin McLeod.
Less than a minute later Cureton did well on the right and found Marcus Bean whose cross was headed wide by Furlong.
Furlong made amends in the 72nd minute, racing on to a long ball over the top and holding off Wotton before the lobbing keeper Luke McCormick.
Gallen sealed Rangers' victory by slotting home in the last minute after McLeod storming run over the left.
Sub Mario Keith netted a consolation goal for Plymouth from eight yards.