Issue with the Connect Line Tool

[micheus]

I am getting a strange extrusion

I just realize that you got that strange geometry for the rear wheel gap by making extrusion to inside of the model.
If you take a look on that fist car tutorial I linked, you will notice the guy uses a best way to do that without get the bed geometry.

About your last post, I just told I can delay to try answer you, not I wouldn't do that.
Also, I'm sure other users can try to help you too.