I purchased a painless wiring harness. Almost everything is connected. When I get to ecu compartment I have the two plugs that insert into the ecu which is common sense. There are three other connectors in that ecu harness and I have no clue what they are for and painless didn’t send anything in the kit that would connect to said connectors. I just need to know if I need them. If I do how do I acquire new connectors?

1987 Camaro with the "F" Engine?
From the image, this car has an Automatic Transmission...

The connector in the Image is the C221 Electrical Connector.
If you look carefully at the Connector-Body, you will see that the Terminal locations are Lettered "A" through "F".

The Connector Pinout is as follows:
-A Even Fuel Injector Power from INJ2 Fuse (Pink Wire with Black Tracer).
-B Unused with Automatic Transmission. ONLY Manual Transmission Reverse-Lights (Light-Green Wire).
-C Power from the FP/ Fan Fuse (Fuel-Pump/ Cooling-Fan) to Cooling-Fan Relay(s) (Brown Wire).
-D Odd Fuel Injector Power from INJ1 Fuse (Pink Wire with Black Tracer).
-E Unused.
-F Unused with Automatic Transmission. ONLY Manual Transmission Reverse-Lights (Dark-Blue Wire).