After taking off the air filter housing I noticed an electrical connector underneath it that is not connected to anything... I'm wondering if it is supposed to be connected to something. I have tried to attach two pictures to help. Here are the identifying features
1: Two prongs
2: Has retainer attached meant to hold it onto a bracket
3: Has Black/Red and Green/Yellow wires attached
4:Comes out of a large wire bundle going from the left of the car to the right at about the spot where another large wire bundle going front to back crosses over.
5: It is on a '93 626 with 4cyl and automatic transmission.

 

Generally wiring harness' are generic. Especially in an older car. They only make one harness per body. So they use the same one in all of them. By the looks of that connector it has never been connected to anything. Likely it was capped from the factory and someone pulled the cap or it fell of. I doubt it is supposed to be plugged in anywhere.