I recently bought an 2004 silverado rcsb. Pretty standard Am/Fm/CD unit, no on star or navigation or anything. The radio reception isn't very good. the seek rarely ever will find a station that works. When I am listening to a station they usually come in unclear. CD player works fine. Any ideas on what it might be? I'm thinking it may have something to do with EMI on the antenna because when i unplug my GPS it get noticeably better.