There are hundredsssssssssssss of EAs on here and every other trading forum that are profitable if used correctly. The market dynamics change almost every week. For example, over the past few months, typical mean reversion scalpers (you pick them, there are tons of them fro Euromaster to Newtech to FAPTurbo etc etc) during late New York session into early asian session have been getting decimated. We see 20-40 pip moves with no more than a 2-7 pip pullback. Why would you try to fade these moves? Why not put on a trend-following system and just go with the flow? But what happens if next week we go back into a consolidation mode during these times, how long will it take you to identify the change in market dynamics?
On top of the technicalities, chances are you are under-funded as well.
Your best bet is to find 3-5 systems on here and run some statistics to make sure they are not correlated and just run them as a basket. Target 1-2% a day. Don't get greedy. Use an equity closure EA to manage the profits and once you achieve your basket equity gains for the day, shut it off. And once you hit your loss for the day, shut it off. If you're running a martingale you absolutely, positively must have an emergency equity stop out. I don't care if you have a direct line to Saxo Bank and you're talking to their desk and there's an order coming in to sell 20k lots of EURUSD. It absolutely positively doesn't matter what you think you know you MUST MUST have an emergency stop out. Long Term Capital Management was sure the market was coming back after a 3 sigma move. Stat Arb works until that cointegrated basket reaches its maximum capacity, when it goes nuclear killing anyone in its path.