That is what Forex Brilliance authors think too and they have created a suit of EAs that trade on specific major pairs. There’s no bafflement as regards what to trade it on and whether it should work better on one pair or another. I think more developers should use this practice. Not only that, when you are trading by hand you should consider that for your manual system too. It is a matter of chance, after you test and change a system on one major pair, it’s sure to perform best on it. Naturally, I do not say that there aren’t any systems that are universal, but it’s’s a lot more difficult to develop and run such a system.