As black in that line I would tend to play 4 ... Nf6   as I feel the immediate capture is giving to much of a positional advantage to white for a single undefended pawn.  Just a little thing I would make sure you're aware of.

However, very nice play against the computer! Curious what the move speed was?

 Hello,

I played against an Excalibur portable, it is set to an advanced level (FH015) where it makes a move taking up to maybe a minute or two, and I have unlimited time, but I made moves in as few as 10 secs up to some where I gave it a good think at about 1 minute. I did'nt time my speed, so these are estimates. Trying to work my strength by playing up levels. When I start winning a lot I bump it up a level. I was getting killed on this level, but then something snapped into place and I turned the tide, so to speak.

I notice I play a better game against the computer when I find some reasonable strong mainline alternatives and occasional out of book moves at the right place. I  have tried combining some ideas from different openings for some games, like a mixed Nizmo/QG hybrid where I use the Bg5 vs Nf6 pin to create an interesting opening alternative.

I think 4...Nf6 seems good, it could get 5.Bg5 as a pin, with 5...h6 suggesting a trade or a play for the expansion manuever 6.Bh4 g5 7.Bg3 with some equality but a lot of space around the black king.