Going back to my look at Informator 26, I've seen a number of interesting pawn advances in games. Here's my favourites from Informator 26:
Ok, for starters white has a promising position in the game Marjanovic-Forintos Kirovakan 1978 with 2 tempting pawn advances in the middle of the board. 18.e5! This pawn break comes with a big tactical threat: 19.Nxh7 with g6 a big weakness. The point of the move was both to engage the enemy and open lines for an attack on the b1-h7 diagonal. Black's position is critical and he felt he had to give an exchange by 18..Rf5 to stop the oncoming attack, but white just took it, regrouped, exchanged and won in technical fashion.
Here we have the great Victor Korchnoi playing black at the 1978 Olympiad against J. Diez del Corral from Spain. Always a fighter, Korchnoi advanced in the centre with 16..d5! Black feels that any opening of the centre will be good for him as that's where white's king is. He also had to calculate the line 17.exd5 Qxd5 18.Bxf6 gxf6 19.0-0 exd4 20.cxd4 Rfd8 when white is struggling to defend his d-pawn and other weaknesses around the board. So as well as threatening the opening of the centre, black equalises in the centre and protects his knight.
Here white was the famous attacking Grand Master, Velimirovic against GM Janosevic. It was black who first got a pawn break in. 16..d5. This is a typical move, trying to break the Maroczy style fortress that white has set up in the middle of the board. I'm not sure black was ready for the pawn break back again that came. 17.f5!. This move engages black's king side initiating attacking prospects, it challenges the pawn chain f7-e6-d5, attacks a knight, opens the c1-h6 diagonal and threatens to open the f-file. Black took 17..exf5 [17..d4 18.fxg6 dxe3 19.gxf7 gives white a massive attack] 18.Nxd5 fxe4 19.Nxe7+ Nxe7 20.Bf4 when white's pieces are incredibly active in compensation for his pawn deficit. Black managed to salvage his king side only to be overrun by white pawn's majority on the queen side.
And finally, the best till last. This was the deciding game in the 1978 World Championship match, with Karpov white against Korchnoi. It is a Modern/Pirc type position and Karpov won in fine style after the pawn break 25.e5! Like before, this engages black's structure, it challenges the pawn chain e7-d6-c5, attacks the knight on f6, opens the b1-h7 diagonal which is important in the line 25..Nfxd5 26.Nf5+!! gxf5 27.Qg5+ Kh8 28.Qxf5 when mate will happen on h7. The game continued 25..dxe5 26.Qxe5 Nxd5 27.Bxb5 Ra7
The moral of the story is keep on the lookout for pawn advances around the middle of the board. Funnily enough, even if they're not fully sound, they are unnerving moves which tend to take the initiative, which may be worth the investment of a pawn anyway (like in Velimirovic-Janosevic).