So with all the different ECU's out there ( black label, pink label, white label, different part numbers, etc) Is there a definitive way to tell if you have the correct ECU installed. Specifically I would like to know what is the correct label and part number ECU for a 1990 240 DL sedan, automatic, with the EZK-116 ignition module.

 

I don't know complete part numbers but Volvo switched from LH 2.2 Jetronic FI to LH 2.4 Jetronic FI in 1989. Those first LH 2.4 had "pink label" ECUs with the part number ending in 561. Those had reliability issues with the fuel pump circuit and therefore they released a new "white label" ECU with the part number ending in 951 somewhere in 1990. The 951 ECU is a drop in replacement for the 561 as the fuel injection version was still LH 2.4. Sometime in '91 Volvo switched to LH 3.1 on some models but which ones, I don't know.

Your car is a '90 so I would recommend using the ECU ending in 951. I'm sure if you google it you can find more detailed part number info.