So I have updated the link to the Evo-DSM Schematic in the How to. I apologize for the How to being rather non inclusive however it isn't really something which can be done step by step but instead requires a good deal of reading and understanding.
As far as the corrections I have made in the How To concerning the changes to the schematic, they are correct. The issue was that there were two schematics posted on EvoM. One was for the 90 ECU and one for the 91-94. My problem was that I found the 91-94 schematic confusing, so instead, I simply noted changes between the two and corrected them textually. To clarify the issue with the ISC, it is quite possible that either way would work. That is that since the ISC is simply a coil, having it connected using either of the schematics would probably allow it to function. Regardless, the actual wiring did change in the model year switch from 90 to 91 and the wires became reversed. That is noted near the bottom of the post above the OBDI picture.
Evo 18-DSM 67 - ISC Coils are reversed but the jury is still out on if this matters.
Evo 5-DSM 68 - See above.
The 90 diagram has Evo pin 18 going to DSM 68 and pin 5 going to 67, but as I said, they are reversed from 91 on. The only other change which must be addressed is the MAF Reset which I also noted.
Evo 19- DSM 6 - 90 to 91 changed the wire for the MAF Reset from 14 to 6
If you notice in the schematic posted here UPDATED LINK TO SCHEMATIC
you will see the 90 diagram has pin 19 going to DSM 14. This simply needs to change to DSM 6.
I am currently pulling the block out of my Evo at the moment but if I can find time this weekend I will post an updated .xml file I use with ECUFlash which has many of the needed mods already entered. These modifications are for things like the rear O2, EGR, etc. It also has the Periphery bits already enabled and the immobilizer code already set to a null state. You won't be able to actually view any of these changes without an actual map to view in ECUFlash, so I will also post a non tuned version of my map which can be pulled up in ECUFlash so you can get an idea what I am talking about. If Hertz or one of the mods is reading this, it would make this a lot more accessible if I could somehow upload the documents to the site instead of linking to them since I don't have any way to make them available.