Can you help with Gringo?

[Daddyg3042]

So....I've taken on a challenge and I'm falling a bit short. We're doing Gringo, a Bill Payne/Little Feat song off of Hoy Hoy. Always loved it and wanted to tackle it. I'm pretty good with most of it, but am getting hung up on the "interlude" beyond the bridge, if that's what that part is called. It comes up at around 3:10.

 

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The beginning of it is a variation on a riff that repeats throughout the song with the chord structure of C F Bb C. At around 3:46 it starts moving into way different territory. I'm getting something like Db to an Ab to a B to an Eb. The riff seems to remain the same but changes key. I've yet to find any chord charts on this part, nor any sheet music. I'm as interested in the chordal movement as I am trying to play it, so I'm wondering if anyone has done it, and what your take on it is. Any insight would be very helpful, and very much appreciated. TIA!