Have a wiring 2005 Grand Marquis w/ Premium stereo setup.

Am replacing it w/ a new Pioneer unit which has latest playback options.

I've already made the connections with an adapter for the speakers and power, but don't know what to do with the small square connector which I think is for the Premium system. It has an 8-pin connector, w/ four wires out, one brown w/ a red stripe, one orange w/ a black stripe, one unshielded wire (probably ground) and one greenish wire w/ purple stripe. (not necessarily in that order.)

Those four are in the bottom spots. Nothing above them.

The adapter from an after-market supplier has six wires out of an 8-pin connector. Four of those are to RCA connectors; the other two are marked "Amp Turn-on", apparently for an amp added to the system.

What I need to know is, what are the pin-out assignments for the original harness? and how do they interface with the new connector that the RCA plugs connect to?

I've not been able to find anything on these connections anywhere.

Thanks for any help.