The Giuoco Piano after 4.c3 Nf6 5. d4 exd4 6. e5 [FEN ""]    
  1. e4             e5            
  2. Nf3            Nc6            
  3. Bc4            Bc5           
  4. c3             Nf6          
  5. d4             exd4
  6. e5


I've faced this line as black a couple of times. Unfortunately all I know about this line comes from Burgess's The Mammoth Book of Chess, where he treats this in a couple of sentences: he says it can be highly effective at club level, and that black needs to find the counter-thrust 6...d5 to get a satisfactory position.

My question is, what does black do after 6...d5 7. Bb3? One of my opponents confidently played that against me. I was out of book, played 7...Ng4, and he developed a strong initiative. Now that I check the position with an engine, the engine suggests 7...Ne4 8.cxd4 Bb4+ 9.Bd2 Nxd2 10.Nbxd2 Bg4 and evaluates as a very small advantage to black. However engine analysis is just a bunch of lines, not very human-comprehensible.

Can anyone familiar with this line give me some pointers on how to treat this position?
(Answering my own question since I got some help from an expert)

Bb3 is a weak move, since the game will soon be focused around the d4-square. White should have played 7. Bb5, pinning the knight. Playing Bb3 instead yields an inferior version of what happens next.

e4 is the best post for the knight - it's a central square, and it's defended as well. Now white has to play 8. cxd4 or he'll be down a pawn. Black responds with Bb4+. The aim of this move is to force a minor piece to d2, which interferes with the queen defending d4. After 8...Bb4+ 9. Bd2 Nxd2 10. Nbxd2, black plays Bg4 pinning the knight and making it very difficult for white to defend the d4-pawn. If white plays 9. Nbd2 instead black can just continue with Bg4 and leave the c1-bishop to stew.

Now white's position starts to get unpleasant. In addition to Nxd4, black threatens 11...Bxf3, ruining white's pawn structure (11. a3? Bxf3 12. Qxf3? Bxd2+ 13. Kxd2 Nxd4 wins a pawn since 14. Qxd5?? Nxb3+ wins the queen). White has to play 11. Ba4, which shows why 7. Bb5 occupying the diagonal sooner was the correct move. Black's position is still preferable: white's knights are pinned, and after 11...O-O 12. Bxc6 (forced) bxc6, black is ready to play ...c5 contesting the center. In the final analysis position below, black has more space, the initiative, and the bishop pair.

[FEN ""] 
     1. e4 e5 2. Nf3 Nc6 3. Bc4 Bc5 4. c3 Nf6 5. d4 exd4 6. e5 d5 7. Bb3?! Ne4 8. cxd4 Bb4+ 9. Bd2 (9. Nbd2? Bg4) Nxd2 10. Nbxd2 Bg4 11. Ba4 (11. a3? Bxf3 12. gxf3 Ba5) O-O 12. Bxc6 bxc6 13. O-O c5


As to what happens after 7. Bb5 ... that's another question entirely =)