My '01 W22 with 28000 miles passed the Maricopa County (Phoenix, AZ) emissions testing today with flying colors, $19.
They remove the gas cap and place it on a pressure testing system, check for catalytic converters, evaporative system (which they couldn't see), and PCV valve (which I don't think they actually looked at), and checked both exhaust pipe emissions at idle and 40MPH dyno test. Funny when they asked to see the engine but not from the dog house (not much to see there).
I wasn't too excited about being in the passenger's seat with the dual wheels spinning in place. I had thoughts of it breaking loose and taking flight.
All that I've done in the 2 years I've owned it is replace the plugs, wires, and changed all fluids to synthetic.
I guess my worrying last year about the exhaust smell (which is still annoying) has nothing to do with proper operation and must be the local blend. We don't have vehicle safety inspections here like some states.
Hydrocarbons PPM: Loaded 75 of 300 allowed, Idle 174 of 300
Carbon Monoxide IN%: Loaded .67 of 3.00, Idle 1.33 of 4.00