Collector Plates only need the low and high idle test, not the driving test.
I I have a 235 and rebuilt my single barrel rochester ($15) and turned the mixture down (leaned out) till it just stopped backfiring. I also had a sticky throttle assembly on my carb so it was idling high. If you gave it a quick kick, it would slow down. Aircare staff are not allowed to touch anything for the slow idle, so if something is sticking and causing it to rev higher than you want, too bad. Added a bit of extra tension to the spring and it passed Aircare at a ridiculously low level. New fuel and nice and warm is also a big help (just like the others have suggested.
They take into account the age of the vehicle so it doesn't have to meet todays emissions levels.
