Audio Systems: Bypass Internal Amp, donor car, color codes

Question
Kelly, I'm trying to use my OEM CD/Cass combo HU from a 99 Camry in my older 96 Camry (it's OEM cass deck died).  The 99's HU has an internal amp, while the 96 has a very good external amp that I'd like to employ.  The 99's has two connectors (10-pin and a 6-pin).  The 96 also has an amplified 10-pin and a 6-pin.  When I hook the combo HU up to the 96's connectors, there's only LOUD squelch (no real audio-just noise).  Hooking up the original cass deck will play through the radio without any problems.  I'm guessing there's some wire that's causing the interference.  Or is this not possible--bypass the combo unit's internal amp?

Answer
Don't bother trying to use the external amp, with the newer head unit. The easiest solution is to remove the old system entirely, and just use the newer HU. If the plugs are different, go to installdoctor.com and look up the wire color codes and get the plugs out of the donor car.
Looking at the diagram, seems they should be the same.