Nitrous Help..Experts come in. Pics inside

Ok I bought a used complete NX nitrous kit and I'm in the process of installing it but I can't figure out what the connection on the bottom of the Nitrous Solenoid is for. I circled it in red on the pics, I thought maybe that the Gauge cable went there but it don't fit.

Also the one I circled in blue is where I'm installing the Purge system.

Thanks