So about a year ago I followed the instructions in the FAQ, thereby successfully the cable I purchased from Radio Shack. It worked, didn't sound so bad, so I thought that was that.
Recently I've noticed a degradation in sound, so I did some testing and found out that a.) I had the channels switched (left & right) and b.) one of the channels now sounded terrible (no bass, voices were muted to the point of essentially being unintelligible). The reason the channels were switched is that my wires are the exact opposite of those in the FAQ (like others have experienced) and the sound was poor as the cheap-o crimp-style wire splicers I had used were coming loose.
Bottom line, I'm gonna redo it and make it right. My soldering skills lick monkey balls, but I want a secure connection. To that end, I'm going to replace the crimp connectors with Posi-Tap Connectors. I've used Posi-Lock™ products on my motorcycle and they are legit. The only remaining issue is, I don't know the gauge of the OEM wiring. The wiring is small (diameter), which makes me think it's 18-gauge or something.
So, does anyone know what gauge of wiring the OEM radio uses? Specifically I'm dealing with the wires were the left/right wires need to be spliced into the system. Just want to make certain I order the correct Posi-Tap Connectors.
I believe there are basically three main issues to watch out for when doing this mod:
1) Make sure to get the left, right, ground, etc. correct for YOUR car, not what a FAQ said or Jim Bob told you. It would appear they are not all the same. Blame GM.
2) Watch out for stray wire strands causing a short path.
3) DO disconnect from XM. The principles of input impedence dictate that you shouldn't just "tap into" the XM wires, but replace the XM output with your input.
If you follow these, the quality SHOULD be perfect.