Brookes had to settle for second behind the returning Byrne in race one, but there was to be no denying him in race two as he came through to take it.
With Byrne leading effectively from the off, Brookes stalked his opponent before making his move with two laps to go before going on to win at the last chicane.
The result ensures that Brookes leads the overall standings by two points ahead of Byrne, while Tommy Hill is a further 20 behind after being edged into third in race two by Alex Lowes on the line.
All eyes were on defending champion Hill ahead of the start of race two, with the Swan Yamaha rider on the grid unharmed after an unfortunate incident prevented him from competing in race one.
However, it was team-mate Noriyuki Haga and Showdown rivals Byrne and Michael Laverty who were neck and neck upon the completion of the first lap.
Rapid Solicitors Kawasaki rider Byrne was the one to take the lead for three laps before Laverty, who opted for a harder rear tyre after falling through the field in race one, made a move.
As in the early stages of race one, Laverty and Byrne traded positions with the Samsung Honda rider eventually holding him off to lead at the start of lap five.
Byrne was soon ahead again, and this time by nearly half a second, with Laverty and fellow title fighters Lowes and Brookes fiercely battling for the runners-up spot.
At the halfway stage, Hill was ahead of team-mate Haga and into fourth behind Tyco Suzuki’s Brookes and Team WFR Honda’s Lowes with costly errors seeing Laverty slip down the field.
Byrne’s lead was soon in danger thanks to a surge from Australian Brookes, however, and he was doing a good job of holding him off.
Brookes eventually went past Byrne on lap 16, but was trailing at the start of the final lap; however, the Australian made his move for victory at the last chicane.
Byrne gestured towards back marker Aaron Zanotti, who appeared to get in his way as the finishing line beckoned, but Brookes by that point looked to have had it won.
Lowes beat Hill into third while another title fighter Tommy Bridewell was fifth, two places ahead of Laverty, who was beaten in sixth by Haga.
Race two results
1. Josh Brookes (Tyco Suzuki)
2. Shane Byrne (Rapid Solicitors Kawasaki) +0.246s
3. Alex Lowes (WFR Honda) +3.018s
4. Tommy Hill (Swan Yamaha) +3.346s
5. Tommy Bridewell (Supersonic BMW) +9.074s
6. Noriyuki Haga (Swan Yamaha) +9.140s
7. Michael Laverty (Samsung Honda) +9.245s
8. James Westmoreland (WFR Honda) +17.311s
9. Robbin Harms (Doodson Motorsport Honda) +17.633s
10. Stuart Easton (Rapid Solicitors Kawasaki) +18.891s
1. Josh Brookes (Tyco Suzuki) 570
2. Shane Byrne (Rapid Solicitors Kawasaki) 568
3. Tommy Hill (Swan Yamaha) 548
4. Alex Lowes (WFR Honda) 534
5. Michael Laverty (Samsung Honda) 532
6. Tommy Bridewell (Supersonic BMW) 521