My fx35 has satellite radio functionality. However I already have a new XMp3i that I would like to install. I typically like to install an FM antenna adapter so that I don't get interuptions while traveling in and out of different areas. I am unable to find one for a 2008 FX35. Is it possible to tie into the existing antenna with my existing car kit? I know there is a system you can buy, but it seems a bit stiff for $300.