You need to troubleshoot the problem by going through each part of your setup individually until you can isolate the cause of the problem. You mention the word 'feedback'? Is it possible that your EP booster has been damaged and is now shorting internally, creating a feedback loop? Have you tried with the EP Booster by itself without other pedals? Also, have you tried it running off a battery rather than an external power supply? So, you have established this feedback only occurs when the EP booster is plugged in? Does everything sound fine when the EP booster is plugged in but bypassed? What about other pedals, do you get feedback when you switch them on? I'd suggest looking into how it is set up and powered before buying more pedals, not that a noise gate isn't worth considering as an option at your disposal, but you should try and get everything as fault-free as possible before adding anything else. I have a number of high gain pedals (distortions, fuzz and overdrives) and don't have issues with uncontrollable feedback, noise, humming or hissing - even with single coil pickups or high gain humbuckers. I've not been tempted to get a noise gate.