我都找到了您，您还没有找到您自己？
确切地说，是“跟贴回复”：
“请问哪里做Drive Clean Emission test? ”，和
** The condition of your car before testing will affect the testing result, and I assume most Emission test centers bought the same model of test machines.
Conditions mean:
1. Whether your car is cold or not
2. Your car was not used for three or four days
3. You have change engine oil
4. New spark plugs (complete combustion, especially hydrocarbon percentage in exhaust gas)
5. Quality of gas you fill into your gas tank (When I came to Canada many years ago, people told me Sunoco has the best quality of gas, and now Sunoco and Petro Canada merged....), that leaves residue in the engine (like the best crude is from Malaysia and Middle East, crude oil from China has very high percentage of Sulphur and impurities)
When the above are optimized, then, it comes to Catalytic converter (whether the platinum catalyst was covered with carbon soots etc and failed to perform, or because temperature is high, amount of platinum has reduced to the extent that it can no longer convert all CO an NO to acceptable levels)
“要做废气检查，大家说上哪比较好？ ”
I think the difference is whether the workers there allow your car to reach a TEST condition, that makes the difference. If your car was not optimized for testing (things I recommended above), then, ....
Of course, as I have said before, if the test center has a garage next door, or the owner of garage also owns the test center, isn't it there is something called "Conflict of interest" ? That is a GREY area. Of course, there is an option called conditional pass which any certified mechanic can charge the maximum allowable repairs and grant you that condition. The key word seems to be "INTEREST" of some party.
By the way, GOOD luck
