here's a site I found, yeah so what it's mustangs, but who cares. It has good general info.

http://www.jason.fletcher.net/tech/sniffer/sniffer.htm

 

I imagine they probably have some sort of hefty fine for doing something like that to pass the test too...

 

They can tell if you have an exhaust leak by the 02 levels in the exhaust. Some states dont measure that thou. A proper tune and a cat can get you by almost everytime. You want to be lean but not to lean.

 

here in texas putting a hole in or loosening the exhaust to create an exhaust leak would be a safety failure.
pulling the PCV and letting it hang in the air would fail visual emissions.

in some states ignition timing is checked, if its too far from specs it fails.

alcohol doesn't lower CO by lowering the cylinder temps, but it does lower NOx like that.

his A/F ratio chart isn't right.
with everything up to temp with a good strong cat on a good running stock motor i normally see CO in the 0.10~0.50 range at the tail pipe with my machine showing an A/F ratio of 14.6~15.2.
pre-cat CO is higher, 0.60~1.20 normally shows an A/F of around 14.5~15.0

 

Passed emissions yesterday (Enhanced/Dyno Smog)

Granted a 350 isnt too much different from 305, the inspector sent it through as a 305. Timing was at 6* (State max 3*). Passed on about 40% below average readings (Cleaner than average). 4bbl, etc..

Trying to remember readings off top of my head

15Mph
CO (.15Max/.13Avg/.09Me), NOx (1029Max/399Avg/25Me)

25Mph
CO (.13Max/.11Avg/.07Me), NOx (944Max/323Avg/40Me)

Cant remember HC, but again way lower than avg.

Its not that hard if your car is in tune... and not wildly modified.