For the first harness: If you're talking about the black wire, I'm not running a relay. That black wire is the negative side of the 02 sensor heater. The 02 sensor heat already has a relay in the EFI system, I just ground it to away from megasquirt itself, because some connections can cause electrical "noise".
For the last harness: The red wire activates a relay. I can use that relay for anything.. It's just specific to my truck. The green wire is for a GM manifold absolute temp (not necessary) and the other wire is for a wideband O2 (again, not 100% necessary), last an additional ground.
For the 22RE stock, I'm using the existing narrowband sensor. If you're dead broke, you could get away with running a narrowband sensor, but you'll have to be very careful - it should *always* read rich under boost and you'll have to be very reasonable with the amount of boost you run.
A stock 22RTE runs a narrowband, so it shouldn't be an issue - Air fuel becomes very important as you put more load (and push more HP) through the motor.
The wideband I've purchased is an LC-1 unit. Retail is $199. Megasquirt can read it just fine, but it needs to be told that it's a wideband.
The purpose of oxygen sensor (narrow band or wideband) isn't for a display. The ECU actually corrects your air fuel based on what the sensor is reading. Besides, you don't need a gauge - if you've got a laptop, you can monitor oxygen sensor output.
I didn't work off a write up. I worked off of understanding megasquirt, understanding the toyota ignition system and understanding the wiring diagram for the truck.
With the write up, it tells you how to build the same harness that I'm selling. Go to:
www.22returbo.com, click on "custom EFI" - first link at the top, it's a word document.
The "other" connector is called a DB37 - female. Frys does carry it, make sure you get one that has pins you solder and then push in. Do not get the ribbon type connector.
The big advantages to running with stock ignition are:
1) Tach works.
2) AC pull up works. You won't loose your AC.
I don't have a serial port either, I'm using a USB adapter myself... I've even seen posts of some people using a bluetooth adapter on the megasquirt, giving you wireless control..