I have a slightly different version of this same issue I was hoping someone could help with.
My audio amplifier (in the trunk pack) died and i had to replace it with one of the many versions that would work, used off of ebay. After installing I realized that my radio reception was lost... but kept it anyways.
I was thinking that the reception may have already been bad, but that it had gone out before the amplifier, or they had led to one another... blah blah blah... but now it is time to fix.
Im going to dig everything up and clean connections, use a voltage meter on the amp, etc.... but before I do that can someone weigh in on what happens if you put a 2000 or 2001 audio amplifier into 2005, but leave the OEM head unit and antenna amplifier. Should I be experiencing this? Can I fix it?