the short story is that the EPA wanted to test the exhaust of aircraft, and the brake dust from them too, so they needed a car with a high speed ability that could keep up. A 200 mph car that was affordable? Superbird of course. They added measuring equipment in the trunk, and a aircraft to car radio above the ashtray, and only used it for 10,000 miles and less than 9 years before it went to auction.
full story at http://reaganiterepublicanresistance.blogspot.com/2012/07/only-cool-thing-epa-ever-did.html