I just went thru this so be careful where you choose to go.

Just about all my tests for my 1991 300CE has been required at Test Only stations because it is designated a "High Emitter Profile".

I prefer to go to my local AAA club to be tested. Either reasonably or unreasonably I conclude that I'll get an unbiased test and not get a come on for repairs. I guess it is possible if you found an agreeable regular smog testing station that they may be able to goose your car to pass if it is very close.

One key advantage comes with using a Test Only Station. IF you fail, you then qualify for the CAP program which pays up to $500 towards getting your car to pass. You only qualify for this help, if 1) you test at a Test Only Station or 2) you are income qualified.

My car failed NOx miserably. The repair bill for new EGR valve, solenoid, EGR tube cleanout, retest was $820, my share $320.

glenmore
1991 300CE
2000 C280
1990 LS400