That track was from Stampede. I don't remember the name off the top of my head, but it originally played when all the Warlords showed up.
The direction for this episode was pretty solid, Bonney and Vegapunk's scene shows that Tokoro still has it as a director. The art took a very noticeable dive in the second half of the episode though (and I'm not talking about the bit with Bonney de-aging Vegapunk with the Ota-pilled blobbiness) so I wasn't surprised to see that that half was outsourced when the credits rolled around. Thankfully Kitazaki handled the bit with Garp pulling up to say "get in losers, we're going to Hachinosu!" so the episode ended on a strong note.