There are programs that can hide you SL and TP from a broker whether or not you are using an EA.
Many EAs add comments to trades. If this is what you want to hide, you could run the EA on a demo account and use a master-slave trade copier to place the trades into your live account. This will add a slight lag to your trades, so I would recommend against it for scalper EAs.
If you are using a popular EA, a bad broker could have a copy and run it just to be able to anticipate trades and widen spreads. There's not much you can do about that other than to change brokers.