[ADTech]

Try the FM trap first. No use in speculating until that has been question has been resolved. I would agree that FMI is a probable suspect along with other, less easily identifiable RF noise sources. Hopefully, you were hooked up with one of our FM filters and not left to acquire one on your own as both of the potentially available alternatives aren't very likely to help much in your location. Hook the FM filter anywhere between the output of the U/V combiner and the input of the CDA4 that is conveniently accessible.

Skip whatever you're calling the "Flatwave" amp. As best I recall, it's amp is internal any they provide you with a power inserter that has to be plugged into a USB port or power supply.

FWIW, I'd skip ALL amplification, your signals are already calculated to be VERY strong and you may simply be overloading your tuner.