The last time Manly were outright competition leaders in a minor round was Round 25 in 2008 after beating the Titans 28-10 at Brookie (the Scum lost 17-16 to the Knights that round). Even though we won the next and last round 34-16 over Penrith, the Scum won 42-4 over Souffs to grab their second straight minor premiership that was of course later stripped.
2008 had a 3 way tie for the minor premiership, but the points difference saw the Scum originally awarded the title. They had +302, we had +290 and the Sharks had +67 (boy, haven't times been tough for the Sharks since then).
The last time we won the minor premiership and the Grand Final was 1996.