Tom, but it was not engine noise, as you suggest, that caused all the noise problems when using the trunk harness. The clicking noise I experienced was not affected by the engine being turned on or off , and was not affected by engine rpm (e.g. engine whine some people complain about). Rather, the noise was present at all times, whether engine was on or off, and whether the key was at turn 0, 1, or 2 on the ignition. However, the noise was more prevalent when the ignition was turned to 1 or 2 since this activated the steering wheel controls, which I believe added to the noise (explained below).
I think instead the clicking noise was due to electromagnetic interference ("cross-talk") in the bundled set of cables routed between the radio head unit and the trunk-mounted amplifier. Here are my reasons why:
First, it must be clarified that while the trunk harness is located in the trunk and connected to connectors near the trunk-mounted amplifier, the connection actually leads to the radio heat unit, and not the amplifier directly. In other words, the Silverline connection is routed from the trunk (where DICE is located), to the radio head unit (at dashboard), back to the trunk (where amplifier is located).
Secondly, for those of you who have tried doing the trunk interface installation, you have seen a bundle of cables connected to the amplifier in the trunk. This bundle includes cables connecting to the radio head unit as well as to all the speakers in your car. (NOTE: the cable bundle is routed from the trunk to the radio head unit by way of the center console where the shifter is located - I discover this when I opened up the dashboard and shifter console to do the Silverline installation via the radio head unit).
So by installing the DICE unit using the trunk interface harness, you are adding to and becoming a part of the cable bundle. As such, I think the control signals going to the IPOD, the text signals coming from the IPOD, and the steering wheel control signals going to the amplifier, all contributed to generating cross-talk on the speaker wires connecting the amplifier to the speaker.
Long story short (too late hheheh!!), by making the Silverline installation at the radio head unit, the cross-talk is either elimitated or substantially reduced.
Hope this theory/explanation helps some of you avoid the aggravation I went through. Good luck!!