The gen 3 3SGTE don’t use Air Flow meter it use a MAP Sensor to control the fuel on the engine, the stock
Computer control 540cc injectors, if you use a Apexi Power FC you can upgrade to bigger injectors, but you have to use the datalogit or the FC hand commander to adjust this option.

2- You can start you engine using the stock igniter and without the temperatures sensor, this is recommendable to check everything in the ignition connection are fine.

3- Remove the Gen 2 Map Sensor and connect the Gen 3 map Sensor

4- With a big smile in your face remove the Air flow meter.
 
5- Take the diagram and compare the differences in the gen 2 and gen 3 pins.

6-The air flow meter harness it use to connect Air Temp. Sensor (THA) and the Manifold Air Temperature Sensor (THAM) direct to ECU. (There are 4 wires but you only going to use 3)

7- To relocate the wires in the engine wiring harness open the clip, in the plug use a needle to open the mini clip inside and pull the wire.

* Put a name attaches to the wire with tape so you know where is going, in case you got confuse.
 
8- Relocate this wires using you diagram:

  A: Remove the PIM (Map Sensor Wire) and the VS (Air Flow Meter) relocate the PIM
  Wire in to VS hole and leave the VS wire in the air to use for connect the Air Sensor.
 
  B: Relocate the KNK knock sensor in the old PIM hole.

9: Relocate the ignition wires:
 
  A: Relocate the NE (Distributor) in this case you need another type off wire because the head of this wire is too big and don't going to fit in the hole.

  B: Relocate the G2 (Distributor) in this case you need another type off wire because the head of this wire is too big and don't going to fit in the hole.

  C: Relocate the G1 (Distributor) this wire is going to the TVIS hole remove the TVIS wire and leave in the air

  D: Relocate the G- (Distributor) from 16 pin plug and put in the 26 pin plug in the FC Hole

  E: The E1 goes in the same place in both ECU

10-Relocate the wires to:

  A: Relocate the FC (Circuit Opening Relay) in the gen 3 pin diagram hole.

  B: Relocate the TPC (Turbocharging Turbo VSV) in the gen 3 pin diagram hole.

  C: Relocate the RSO in the gen 3 pin diagram hole.

  D: The STJ (cold start injector) is not use in the Gen 3 ecu.

  E: Relocate the EGR in the gen 3 pin diagram hole.

  F: The STJ (cold start injector) is not use in the Gen.

  G: Relocate the FPR (Fuel pump relay) in the gen 3 pin diagram hole.

11- Start you engine, check everything is fine.

12- Install the Manifold Air Temp. Sensor (THAM)

A: Use your air flow meter harness and locate the (VS) wire, attach this wire to the sensor (THAM) and the other side
 of the wire next to the ECU insert to the (THAM) in the gen 3 diagram

Do not connect the sensor ground to the chassis, this can damage the ECU

B: Use your air flow meter harness and locate the (E2) this wire will supply the ground to (THAM)

C: Use your air flow meter harness and locate the (THA) wire, attach this wire to the sensor (THA)

D: Use your air flow meter harness and locate the (E2) this wire will supply the ground to (THA)
You have to use the same E2 engine ground for the 2 sensors,

E: install the (THAM sensor) in your Intercooler Pipe or Intake manifold.

F: Install the (THA) Air Temperature Sensor in your Intake filter.
3SGTE 1991 DIAGRAM