where do they still do this 'sniffer' test? I am a certified NYS inspector, and at my shop we dont do that anymore..as of January this year they did away with all the old inspection equipment. No more dyno roller and road test crap.
All it is now is a plug in to the OBD port. no CEL and 5/6 monitors need to be ready and you will pass no problem. Having monitors at the 'not ready' status (02 sensor, 02 heater, catalyst, secondary air, evap emissions) will cause you to not pass.
I have experienced some flashes on some other makes of cars that just simply disable the rear 02s, and in some cases that permanently sets it to 'not ready'. There are ways within flashing a car that can allow you to permanently set it as 'ready', or program it to feed a dummy signal so it thinks everything is ok.
I do this with the BMW crowd all the time..we have all sorts of little adjustable potentiometers to wire in and fool the DME into thinking it has cats...heck you only need it for less than a day and you can yank it out again.
the 335 crowd was proven to pass smog in CA with catless downpipes but retaining the secondary cats in the exhaust..so for any tree huggers out there, the cars of today put out WAY less emissions than someone whos driving around a 1995 honda civic.