Bobby Fishel and Ben Kersh netted for the Haroldeans before Shiffman took over.
The striker's cameo kept Haroldeans at the summit and boss Bloomberg said: "It was our toughest game so far and we had to dig deep to earn the win.
"But Adam's finishing was superb. He proved the difference and will be key for us this season."
Maccabi Manchester Yellow boss Anton Radiven says his side will be in the shake-up this season.
They lie third in the table and Radiven said: "We have shown that we will cause teams problems and win games.
"It's just about finding that consistency. But the signs have been good."