Performance Chip location
It will be in the DME. The rest of the world calls this the ECU.
If you have an E36, this will be on the passenger side of the engine compartment in the firewall. There will be a rubber cover, and then another cover hiding it just below where the bonnet hits the bodywork.
Once you have everything open, you can unclip the wiring harness and slide out the computer.
Depending on model, it may have tabs or torx screws to open it.
You'll see a chip that is higher than the rest with a plastic cover. If it is an intel Flash chip its standard.. otherwise it will have a special sticker on it.