'89 245 254K: NYC emission...failed, NOx.

test limits HC 0.80 gpm CO 15.00 gpm NOx 2.00 gpm
vehicle reading HC 0.43 gpm CO 5.10 gpm NOx 2.13 gpm

So I leave it with the guy to see what he can do. He calls me a couple of hours later. The car passed...a minor timing adjustment, not much he said, plus a bottle of octain boost. A long-necked red bootle called, I think, Turbo Boost. So the new readings are:

HC 0.46 gpm CO 0.84 NOx 0.01

So what gives? CO and NOx readings this low? NOx is almost non-existant. Is this possible? The car was/is in better than perfect running condition when I first brought it in, so I don't think a minor adjustment in timing would have much effect...but would octain boost effect readings this low? Is this miricle stuff? Or....is this guy manipulating the test somehow? Is that possible? Fraud in the auto repair business...? After all, it did cost me $137 for the so called repairs, timming adjustment, octain boost $6.50, including re-test $27. I kind of feel like spending $27 to retake the test, somewhere else, to confirm these numbers. Can the test be fixed to pass? Fixed to fail? What about this Turbo Boost?