Michal Psurny grabbed a hat-trick as they erased a 3-2 loss by the same side on Saturday.
Phoenix were second best for the opening period and were lucky to be on level terms with a resurgent Flames.
Guildford were on top in all areas of the ice – but the home side just about clung on to their coattails.
Ironically, Tony Hand fired Phoenix after six minutes, against the run of play, before Guildford replied through Ben Campbell.
The visitors should have been further ahead but netminder Stephen Fone and Robert Schnabel were stellar.
Andy McKinney riffled home early in the second period to make it 2-1 but goals from Tom Duggan – his third of the weekend – and Chris Cooke had the Flames deservedly ahead.
Phoenix then simply upped the pace and blew their opponents away.
Psurny scored on the powerplay following Hand’s superb pass then Luke Boothroyd swept home.
And 52 seconds before the end of the second period it was 5-3 as Robin Kovar placed a shot past a bewildered James Hadfield.
The third period saw Hand and Guildford’s coach Paul Dixon in the penalty box for Hooking and Interference respectively but it took until the 50 minute mark for the next strike – Psurny tucking in a rebound from Frantisek Bakrlik’s shot.
Former Phoenix star Marcus Kristoffersson replied with less than four minutes to go but Psurny hammered home his hat-trick late on, from a great Joe Graham feed, to seal the win.
Saturday night’s match was tight until the Flames grabbed the winner with 99 seconds remaining.
James Archer missed a penalty shot late on and unfortunately he was made to pay.
Guildford thought they’d scored in the 16th minute, only for it to be ruled out, but less than 60 seconds later Kristoffersson put Curtis Huppe in for the first.
Duggan notched the Flames’ second at the end of the period but Archer hit a goal back on 23.53.
Schnabel levelled at the end of the second and Phoenix could have taken the lead when Archer was hauled down.
But his penalty shot was saved by Mark Lee and Duggan tallied his second to hand Phoenix their first defeat.
Manchester remain top of the EPL, two points clear of the Flames.
To contact the author email: Mike.Appleton@prohockeynews.com or tweet @mascarandy