Then I happened to go to this site:
http://www.gt350mustang.com/vin.htm
where I got a good laugh, as there was a tiny
bit about NLR, there too. They decided that it stands for
"NO LOUVERS--Rear" at one point a contributer
- referring to the explanation types No Lovers- Rear
So.... why didn't ANYbody ask me ??
NLR = Noise Level Reduction
It was included on Mustangs/Capris that were fitted
with a different muffler system (I don't know what was different;
perhapps a more aggressive sound).
The noise level reduction was some product to bring the
exhaust system down into legal OEM levels of noise,
while still using an agressive muffler system.
It could be add'l. noise reduction in the inner body
panels of the car, more than likely and/or within
the muffler itself.
Put a 1985 Mustang GT next to a 1985 86 McLaren Coupe
and rev the motor up & down to hear that the McLaren has a deeper
and more aggressive tone.
Now I go back to bed. Bad Bad > Big bad Cold.