Chrysler Repair: 87 New Yorker radio problem: where is the power amp?, infinity sound, radio problem

Question
I have a 87 New Yorker Mark Cross edition with an infinity sound system. The volume jumps from quiet to very loud (and back to quiet after a few minutes) while driving. The passenger door speaker also has periods that it blasts out a large static noise. Again this appears at random times and doesn't appear to correlate with the volume jumps. I have replaced the radio and door speaker with an exact replacement form the parts yard with no success (symptom did not change). Also, with the radio powered off, sometimes the dash speakers emit a low "static" sound. Is there an amplifier somewhere? I've searched the trunk and didn't find one. Any help would be really appreciated.

Answer
Hi Mike,
I checked the 86-88 manuals and found one specific reference to the power amp in the '86: "Center of top cowl panel". That sounds to me like it is under the dash in the mid-body area probably at the underside of the pad just behind  the windshield. If there is an unused opening for a center speaker, it might be around there.
You might also find it by tracking where the wire harnesses that plug into the back of the radio go.
Sorry to be slow in responding but the site's server was acting up so I couldn't log on.
Roland