The code sits in one of my archive folders. I ran it for a few years, perhaps to 2004, and saw the market steadily becoming more efficient, lowering my results (like the OP did). It may well be that it no longer predicts skillfully or profitably. As I recall, to beat the market the costs had to be very low, like pennies per trade, with no bid/ask spread, which I understood to be possible for large trading firms.
OK, cool. There are some places that offer equity trading for ~$0.005/share, but that says nothing about overcoming bid/ask. Looks like the OP did that by throwing a bit of market making into the mix.