AylerKupp: <jerseybob>, <Fusilli> My Stockfish 6 also evaluates 15.Nxg5 as White's best move, but only at [-0.75]. Here are Stockfish's top 3 lines at d=35:1. [-0.75]: 15.Nxg5 d5 16.Qh7+ Kf8 17.Ngf3 e5 18.Nh4 Nc6 19.Ng6+ Kf7 20.f3 Be6 21.Rh4 Qg8 22.Qxg8+ Kxg8 23.Ke2 Rf7 24.Re1 Re8 25.Kd1 Bd7 26.Nb3 b6 27.a3 Bf6 28.Rhh1 Bg5 29.Bb5 Be3 30.c3 Rf6 31.cxd4 exd4 32.Rh4 a5 33.Bxc6 Rxc6 34.Nxd4
2. [-0.97]: 15.Qh7+ Kf8 16.Nxg5 Nc6 17.Ngf3 Be6 18.Nh4 Ne5 19.Qe4 Qb6 20.b3 Qa5 21.Ng6+ Nxg6 22.hxg6 Qg5 23.Rh2 Bd5 24.Qh4 Re6+ 25.Kd1 Qxh4 26.Rxh4 Bxg2 27.f3 Re3 28.Kc1 Rc8 29.Kb2 Kg8 30.Rg1 Bxf3 31.Nc4 h5 32.Nxe3 dxe3+ 33.Kc1 e2 34.Bf5 Rc6 35.Be6+ Kh8 36.Rf4 d5 37.Re1 Rxe6
3. [-1.28]: 15.Kf1 Nc6 16.Qh7+ Kf8 17.Nxg5 d5 18.a3 e5 19.Re1 Qd6 20.Nde4 dxe4 21.Nxe4 Qe6 22.Nxf6 Qxf6 23.Kg1 Be6 24.Qg6 Ne7 25.Qxf6+ Bxf6 26.f4 Nc6 27.g3 Ke7 28.Kh2 Kd6 29.Rhf1 Rc8 30.Re2 exf4 31.Kg1 Ne7 32.Rxf4 Be5 33.Rfe4 Rc5 34.Re1 Bf5 35.R4e2
And after 15.Qh7+ Kf8 16.Nxd4 (which is what I assume you meant, aiming for f5 as you indicated) Stockfish at d=32 evaluates the following 3 lines as being best:
1. [-2.52]: 16...Qb6 17.Nf5 Bxf5 18.Bxf5 d5 19.Bd3 Rxf2 20.Be2 Nc6 21.Rf1 Rxf1+ 22.Kxf1 Qxb2 23.Nb3 Nd4 24.Rd1 Nxe2 25.Kxe2 Qe5+ 26.Kf1 Rc8 27.Re1 Qf6+ 28.Kg1 Rc4 29.Rf1 Rf4 30.Qd3 Rxf1+ 31.Qxf1 b6 32.Qxf6+ Bxf6 33.Kf2 Kf7 34.g4 e5 35.Ke3 Be7 36.c3 Ke6 37.a4 Bc5+ 38.Nxc5+ bxc5
2. [-2.10]: 16...d5 17.Bf5 e6 18.Bh3 Qb6 19.Qd3 Rf7 20.c3 Nc6 21.Nxc6 bxc6 22.Rb1 Rxf2 23.Qg3 Rf4 24.Rf1 Rxf1+ 25.Nxf1 c5 26.Kf2 Bd7 27.Kg1 Kg8 28.Qe3 Rb8 29.Nd2 c4 30.Qxb6 Rxb6 31.g3 Be8 32.Re1 Rxb2 33.Bxe6+ Kf8
3. [-1.94]: 16...Nc6 17.Nf5 Bxf5 18.Bxf5 Qb6 19.Kd1 Qa5 20.Bd3 Rxf2 21.Ne4 Rf7 22.Rf1 Rxf1+ 23.Bxf1 d5 24.Nd2 e6 25.Qd3 Qb6 26.Qb3 Qc7 27.Qh3 Rd8 28.a3 Qf7 29.Qf3 Bf6 30.g4 Ne5 31.Qb3 Kg8 32.Be2 Rf8 33.c3 Bg7
Black's LSB prevents White's knight from staying on either f5 or e6, and White's Nd4 can soon be challenged by ...Nc6.
Komodo 8 provides similar results, here are its top 3 lines at d=28:
1. [-0.61]: 15.Nxg5 d5 16.Qh7+ Kf8 17.Ngf3 e5 18.Nh4 e4 19.Bxe4 dxe4 20.Nxe4 Qa5+ 21.b4 Qe5 22.f4 Qe7 23.Ng6+ Rxg6 24.Qxg6 Nc6 25.Kf2 Nxb4 26.Rae1 Nxc2 27.f5 Nxe1 28.Rxe1 Bd7 29.f6 Qf7 30.Qxf7+ Kxf7 31.fxg7 Kxg7 32.Rd1 Rf8+ 33.Kg3 Bc6 34.Rxd4 Rf5 35.Nd6 Rxh5 36.Nxb7 Rg5+ 37.Kf4 Bxg2 38.Nd6 Kg6 39.Ne4 Rf5+ 40.Kg3 Bxe4 41.Rxe4 Ra5 42.a4 Rg5+ 43.Kf4
2. [-0.81]: 15.Qh7+ Kf8 16.Nxg5 Nc6 17.Ngf3 Be6 18.Nh4 Ne5 19.Qe4 Qa5 20.Qxb7 Rc8 21.b4 Nxd3+ 22.cxd3 Qxh5 23.Kf1 Rc2 24.Ndf3 Bc8 25.Qxa7 Qb5 26.Kg1 Qxb4 27.Rf1 e5 28.a4 Rc5 29.Kh2 Qa3 30.Rd1 Kg8 31.Rd2 Qb3 32.Qa8 Qe6 33.a5 Rf4 34.a6 Qf7
3. [-1.09]: 15.Kf1 Nc6 16.Qh7+ Kf8 17.Nxg5 d5 18.Re1 e5 19.g3 Qa5 20.Ndf3 e4 21.Nxe4 dxe4 22.Bc4 Ne7 23.Qxe4 Qc7 24.Bb3 Bf5 25.Qxd4 Bxc2 26.Bxc2 Qxc2 27.Ne5 Kg8 28.Re2 Nf5 29.Qd5+ Kh7 30.Rxc2 Ne3+ 31.Kg1 Nxd5 32.Kg2 Rd8 33.Re2 Re6 34.Rhe1 Nb4 35.f4 Nxa2 36.f5 Rxe5 37.Rxe5 Bxe5 38.Rxe5 Rd2+ 39.Kf3 Kg7
And after 15.Qh7+ Kf8 16.Nxd4 at d=26 Komodo evaluates the following 3 lines as being best:
1. [-2.29]: 16...Qb6 17.c3 d5 18.Be2 Qxb2 19.Rd1 Qxc3 20.Qc2 Qxc2 21.Nxc2 Rd6 22.f3 Nc6 23.Nb3 b6 24.Kf2 a6 25.g3 d4 26.Bd3 Be6 27.Rhe1 Bf7 28.Be4 e5 29.Nb4 Nxb4 30.Bxa8 Nxa2 31.Nd2 Nc3 32.Rc1 b5 33.Ne4 Rd8 34.Nxc3
2. [-2.07]: 16...Nc6 17.Nf5 Bxf5 18.Bxf5 Qb6 19.Kd1 e6 20.Bh3 Rxf2 21.Bxe6 Qd4 22.Qd3 Re8 23.Qxd4 Nxd4 24.Bc4 d5 25.Rf1 Rxf1+ 26.Bxf1 Nf5 27.Bb5 Ne3+ 28.Kc1 Re7 29.c3 Nxg2 30.Kc2 a6 31.Ba4 Ne1+ 32.Kd1 d4 33.cxd4 Bxd4 34.Rc1 Nd3 35.Rc8+ Kg7 36.Kc2 Nxb2 37.Bb3 b5 38.Bd5
3. [-1.93]: 16...d5 17.Bf5 e6 18.Bh3 Qb6 19.Qd3 Rf4 20.Ne2 Rxf2 21.c4 Nc6 22.Qa3+ Kg8 23.c5 Rxe2+ 24.Kxe2 Qb5+ 25.Kd1 Ne5 26.g4 Nd3 27.Bf1 Qxb2 28.Qxb2 Bxb2 29.Rb1 Nf2+ 30.Ke1 Bd4 31.Nf3 Bxc5 32.Rg1 b6 33.Rg2 Nh3 34.Rc2 Nf4 35.Ne5 Kg7 36.Nd3 Nxd3+ 37.Bxd3 e5 38.Rg2
So according to these 2 engines it doesn't seem that after 14...Rxf6 Guimard had the better game, let alone a win. And 15.Qh7+ Kf8 16.Nxd4 does not see to hold much promise for White.