23...Ba6 24.Nf6+ Bf6 25.Qh7+ and black is in very bad trouble.

The point here, i guess is that the white bishop is very dangerous and needs to be removed letting the queen assume a seemingly strong position only to harass her the very next move by Ba6!!

It looks like 31. Rf2 preparing to sacrifice the exchange is met with Rxb1+ and Qd4+.

For what it is worth, Hiarcs tells me that in the final position white has a forced mate in 10. For example:

31. Qxe7 Nxe7 32. Rxe7 Kg8 33. Re8+ Kf7 34. Rc8 Rxc8 35. axb4 Rc2 36. Ne4 Qc1 37. Nd6+ Kf8 38. Nc4 Rxc4 39. a3 Rc2 40. h4 Qb2#

Finding the initial move may not be insanely difficult, but the follow-up could be a bit of a challenge.

Here's a bit of analysis verified with Fritz 8:

<23...Rxd3!!> Decisively weakening White's Queenside castled position with a surprise demolition.

<24. Qxd3>

[24. cxd3 Qc2+ 25. Ka1 Qxd1+ ;

24. Nxf6+ Bxf6 25. Qxd3 (25. cxd3 Qc2+ 26. Ka1 Qxb2#) 25...Ba6 26. Qe4 Bxe2 27. Rc1 (27. Qxe2 Qxc2+ 28. Ka1 Qxb2#) 27... Bxb2! 28. Qxe6+ Kh8 29. Kxb2 Qc3+ 30. Kb1 b3 31. axb3 a3 ]

<24... Ba6! 25. Qxa6 Qxc2+ 26. Ka1 Qxd1+ 27. Nb1 Rc1! 28. Ned2>

(28. Qxe6+ Kh8 29. Ned2 a3 30. bxa3 Bc5 31.
Qc8+ Ng8 32. Qd7 bxa3 33. Qd3 Qc2 34. Qxc2 Bd4+ 35. Qc3 Bxc3#)

<28... a3! 29. Qxe6+ Kh8 30. bxa3 Ng8> 0-1

White resigns in the face of nothing but losing possibilities, such as 31. g5 (31. Qe5 Bf6 ; 31. axb4 Bf6+ ) 31... Bxg5 32. Rf2 Bxd2 33. Qe4 (33. Qe2 Rxb1#) 33... Bc3+ 34. Rb2 bxa3 35. Qc2 axb2+ 36. Qxb2 Rxb1#.

Material B for N. Both sides are set to attack the opposing K, but Black's pieces are better coordinated and are assisted by Pa4 and Pb4. White has a hidden back-rank mate threat, Rd1 is unprotected, Bd3 is overburdened with Pc2 and Ne4, but Bd3 is also aggressively placed to aid the Qh3 in attacking Ph7, which with Pe6 is a weak point. The Bd3 is presently worth at least an exchange.

Candidate moves: Rxd3, Nxe4, Bxe4, a3, b3, Qf4, Qe5, Qc2+

I find it helpful to list even low priority candidates, to increase my awareness of them.

The back-rank mate threat in particular suggests thinning the pieces in the center to expose the threat. Note: right now, Rxd3 must be answered by Qxd3, to maintain protection of Pc2. Move order is exquisitely important, because Nxf6 is with check and takes priority. A hanging piece at e4 is desirable in some lines.

23...Nxe4 24.Nxe4 Rxd3 24.Qxd3 [cxd Bxe4 25.Rxe4 Qc2+ and #, so White must submit to losing B+N for R] Rd8, and because of the threat Rxd1+, White loses Q+B for 2Rs.

24.Bxe4 Bxe4 25.Rxe4 [Nxe4 Rxd1#] Qxc2+ and 26...Qxd1#

24.Rxe4 Bxe4 25.Bxe4 or Nxe4 25...g6 and White has dropped the exchange without compensation, and the Pa4 and Pb4 can storm to open lines for the extra R.

In the final line, 24...Rxd3 does not seem to work for me any more, but the line given is sufficient anyway. Possibly, 24...Rxd3 leads to a fatal pin on the Nd2, but it is unnecessarily complex. Time to peek.

Ba6 was a nice touch, where I was aiming to produce hanging pieces at e4. Today's puzzle reinforces my conviction that I miss best solutions by not considering all candidate moves. Time to check the kibitzing.

CM preferred the in-between move. 28.Nxf6+ gxf6 [as you said not 28...Bxg6 29.Qxe6+ Kf8 30.Qe2++] 29.Qxe6+ Kh8 30.Qe4 Rxb1 Qxb1 31.Qxe2 was my continuation.

23...Nxe4 24.Nxe4 Rxd3 24.cxd Bxe4 25.dxe