Just had a new deck/amp/speaker install to replace my gradually failing stock items. weirdly enough, the only thisng that worked well with the factory unit was the radio. with the new pioneer unit, all is well except for the radio signal. I brought it back to the installer who checked to make sure the antenna was connected and to look for any other possible loose connections. He found no glaring issues. He also spoke to a number of his colleagues to see if they had experienced this problem. He was also asking around the install groups to find out if there was some sort of FM amplifier built into the wiring harness. Since he couldn't rectify the situation he asked me what I wanted to do and he ultimately rebated me a portion of the install.

Does anyone here know of a reason why this would happen? '96 850 wagon with integrated window antenna. I scoured the FAQ's with no success.