Oh, I don't know of any public domain schematic of the internals.
If you look in the Mega Manual I believe it has a description of the signals there.
Also some pinouts for the ECM will have what the the signals should be on those wires. So look at TBI pinouts charts, not the schematic. You shoudl be able to find some of those in the '7747, '7427 and other TBI therads found on this site in the GM hardware forum (a sub forum of this very forum).
Basically though, The Black/red is ground so there should be near zero volts on it, the tan/black is the bypass and should have 0 volts when off or cranking and 5V when above 400 (or so) RPM, the white and purple/white are signals too and from the ECM and have TTL level pulses IIRC on these. The signals vary based on RPM and commanded timing. The pink is 12V ignition and the white paired with the pink is the coil trigger that will have an AC signal on it, I just don't recall the magnitudes or exact wave form off hand.
Basically if it's working, then it's wired correctly. Swapping any of the pins on the ICM will cause a no run condition.
Get rid of the resistor wire, and your idle should smooth out then. The GM ICM and coil needs a full 12V to it, not through a resistor wire.
The 12V feed to the distributor being connected to the coil is how GM did it, so that is not of concern.
Bookmarks