Miata Minimum Wiring Harness - questions about repercussions/re-using removed ECU pins? (MSPNP2)

So in the interest of less is more I've paired down my wiring harness to what I believe is the true minimum for my setup.

I've decided to move to a pi-dash setup so I could finally remove the huge dangling pile of wires that ran to the dash. With this current setup the under dash fuse panel has a whopping 1 fuse (for the ecu) in it.

So removing most of the dash/diag port wires was straight forward, but while doing that I found that I had terminated 11 wires that run to the ECU - I've checked them before depinning the harness (i.e. I can easily put them back on), but it had me wondering if I can re-use them if I modify the code for the MSPNP2 ? I'm a software engineer by trade and have worked with firmware/software for a while now - while setting mine up I found several instances of individuals modifying/building the firmware from scratch and enabling new functionality - does anyone have a good starting point for that?

Question 2 is did I mess anything up by removing any of these? When pairing the harness down I always start the car and check everything between each removal, but obviously there are a lot of moving parts. Notes - I've remove AFM long ago - so just the temp sensor remains.

Here's the depinned list (http://neomiata.com/garage/Wiring%20Diagrams/Wiring%20Diagrams%201990-1996/1990_Miata%20Wiring%20Diagrams.pdf):

#2 X - Ylw/red purge valve
#2 K - lght grn/red AIR FLOW METER
#1 F - wht/yellow diag port
#1 Q - lght grn/ black diag port
#1 E -  Ylw/blck dash check engine light
#1 A - blue/red room fuse
#1 D -  White/green diag port
#1 S - blue/orange heater control unit
#1 U - red/black tail fuse
#1 J - blue/black a/c relay
#1 O - green stop light sw

As far as I'm aware (and please note it's been well over a decade since I looked at it with the MS1s), you can change any input other than the actual power/switched power/ground into your MS, although lots aren't practical to switch due to circuitry such as the injector drivers.    Almost all sensor inputs operate on some variation of 0-5V or 0-1V signals, or a resistance check (temp sensors), so if you can find one of those circuits to use, you should be able to reflash it with a modified firmware that looks at input #34 instead of the default input #19 without too much difficulty.

Hmm, right, that makes sense - I was really hoping to get my oil pressure wired into the ECU since that's not one of the inputs - I think the dash just interprets that signal. I'll have to do some more research. 

I've almost got it wrapped up, I ordered some expandable wiring cover and cloth tape to hopefully make it loo a bit neater this time. I've also added in two fuses (grand total of 3!) - one for the tach, one for the wideband. I'm still pleased with how minimal the harness is now.

Email me at support@diyautotune.com with your MSPNP model number, and I can get a customer pinout for your ECU with all the pins that are populated inside the ECU. A lot of the factory pins aren't used.

In reply to MadScientistMatt :

I missed this response! Will do!