I just installed Sirius in my 05 4.8is w/nav and dsp. Everything works as it should but i'm experiencing drop outs on the Sirius. Happened quite a lot yesterday. I'm in the Chicago burbs so I would assume the signal is strong. I installed the antenna in the rear spoiler first laying down a 4"x6" area of foil tape followed by 3m tape to hold the antenna in place. Should I install a metal (steel) liner instead of the tape? Is the tape causing poor reception? Any info would be appreciated. Thanks