Is this a kind of deferred Benko Gambit $2 If this is so, it's a much-improved version for Black, as the files are opening close to White's king.
1. e2e4  1... c7c5  2. g1f3  2... e7e6  3. d2d4  3... c5d4  4. f3d4  4... g8f6  5. b1c3  5... b8c6 This variation of the Sicilian is very topical lately. As I understand it, Black's idea in the move order with 2...e6 is to avoid the Rossolimo Variation and other options for White and to transpose to the Sveshnikov Defense. But not everything is rosy: White, who has been stripped of his right to play the Rossolimo, can now choose to capture the knight on c6. 6. d4c6  6... b7c6  7. e4e5  7... f6d5  8. c3e4  8... d8c7  9. f2f4  9... c7b6  10. c2c4  10... f8b4  11. e1e2  11... f7f5  12. e4f2 12.exf6 is equally played here, and it's not clear which move is better. 12... c8a6  13. e2f3  13... d5e7  14. c1e3  14... b4c5  15. e3c5  15... b6c5  16. d1d6  16... c5b6  17. b2b3  17... c6c5 There are still hundreds of games played in this position. 18. f3g3 Played after a long thought. Maybe Kosteniuk was out of book at this point. 18... g7g5 [%c_effect g5;square;g5;type;Interesting;persistent;true] An interesting pawn sacrifice. 19. f4g5 