Quote Originally Posted by KeithGTP03 View Post
Are you running an amp for your mids and highs? If not, there is no need to filter preouts that are not being used. Since you've checked the grounds, the last thing I would check is your sub amp. Remove the rca's from the amp and see if noise goes away. You may be getting a feedback usually caused by the rca's ran next to a power line. If the noise remains, return the HU.
I have the monsoon system so it comes with a factory amp for all the speakers, but the speakers are connected with rcas at the front with the deck.