Plymouth Voyager With Infinty Package?

I own a 1992 Plymouth Grand Voyager, 3.3L AWD with the cassette stereo with the Infinty sound package. I am attempting to install a pioneer CD deck. I bought a harness so I don't have to cut into the original Plymouth harness. I can get the front speakers to work but the 2 doors and the rear hatch speakers are a problem. The rear hatch speakers, I can get sound from but it sounds like it comming through a telephone. I have tried all sorts of wire combinations to no avail. I can get nothing from the door speakers. I know the door speakers and the front speakers are jumpered together. But I can't get any sound from them. I have a original Plymouth service manual, the big think one, I looked up the radio wiring harness in there. It does not appear to jive with the wiring in my van. Nor can I locate a direct power wire, unswitched from the battery. Has anyone had any experience with this? Any comments appreciated. I get the feeling the door speakers are amplified by built in amps on the speakers. Is this correct? If so how can I get around this?

Keith