I would agree on the bad ground connection. I have the Shaker 500 and installed the Kenwood DNX570HD (2013 model) w/ Maestro RR and have no issues. Sound is better than OEM and so far I love it.
I'm currently using the Metra touch screen dash kit and it's really growing on me, but I would consider switching to the iDatalink dash kit if they ever release the dam thing. Last I heard they were gonna ship in August but it's the end of August and still no update...sigh
Anyway since this post is 4 months old I'm sure you've got this sorted by now but for anyone searching this issue, double check your ground connection!
2010 Black GT. Appearance mods only so far. SS center fog grille, DG Customs side and window scoops, SLP Loudmouth axle backs, Roush center console button, Roush white shift knob and boot, Metra touch screen dash kit w/ Kenwood/iDatalink NAV setup to retain SYNC.
NOTE: OEM grille, mufflers, and 401A shift knob w/boot are for sale if interested. PM me an offer.