Since I have started developing TOYOBD1 I learned constantly about the 90s to mid 90s OBD1 Toyota ECUs, they all share similitudes.The traps we fall into while doing custom engine wiring jobs are also similar here are a few I have encountered through the years that may save you time and money.
The STA wire
STA is not to be fed with a constant 12v source like b+, it's purpose is to inform the ECU that the starter is engaged while the starter is engaged. feeding constant 12v to STA will fool the ECU into thinking it is cranking all the time, regardless of engine speed.this will make an ECU inject about 2.5 times the fuel it would have injected normaly. in all cases I have seen it is so rich the ignition cannot burn all that fuel, and of course engine performance is bad. Lots of people fall into that trap, stay aware!.
The Batt wire
This one is a constant 12v power source, it is fused and always powered regarless of ignition key position. this is what keeps the RAM (ecu memory) powered at all time. not feeding Batt correctly will result in Error codes being wiped every time the engine is shuted off, and the ECU learning process starts form scratch every time.
Digital 3 wire TPS (PSW, E2, IDL)
On cars using this system it is important that those signal be wired correctly. those ECUs dont have a real TPS, this TPS design only tells the computer if you are at idle, at WOT , or anywhere in between. this is a lot of guessing and if the ECU senses the throttle is at WOT when it is not it may take bad fueling and ignition angle decisions. a digital tps can also simply go bad and need replacement. found on MT cars 3S-FE,4E-FTE,etc
The E2 wire
This is a special ground,This is the sensors ground, this ground must not be tied to other ground signals directly, doing so may introduce sensor noise or worst.