emission control module

There is no such thing. The emissions control is a system that is built into the Engine Computer. Part of it has to do with calculating fuel metering and ignition timing to prevent excessive emissions, and part of it has to do with cleaning up what emissions does occur. The Engine Computer is mounted on the left inner fender.

I think it is the ENGINE control module. Somewhere in the vicinity of the coil / distributor area.

The Engine Computer, (Engine Control Module - ECM) is on the driver's inner fender. You didn't say which engine you have or what problem you're trying to solve. If your engine has a distributor there will be a pickup coil in it and possibly a small ignition module. GM used to have a huge problem with Engine Computers in the '80s and early '90s, but by '96 failures were not common.