1975 So Cal "installed Smog Thing"

Interesting... I found a forum for Ford Mustangs that talks of the Nox systems and of plugging the vacuum advance. last year I was repairing the dist in my dart and found the vacuum line to the dist to be plugged with a professional looking plug. I bet it was installed as part of the Nox device being installed and My dad forgot it was there when the Nox device was removed. That explained the drivability issues the car has had off the line for decades. I removed the plug and the engine has no hesitation of the line even with the 5 ATDC timing the service manual recommends.