My 2010 Silverado 1500 LT has a hum thru the l/f door speaker and tweeter if the headlights or parking lights are on, but not during the daytime in auto mode with DRLs on. Anyone hear of this before or have a clue what could be the cause? The him does not change volume or change frequency with engine RPM. I just bought it and everything appears stock although I did see pics of this truck with blackout taillights that were changed back prior to my purchase.