For the past 22 ( ! ) years, I've posted on this thread the results of my semi-annual California smog/emissions tests.
Residents of other states are welcome to post, though I am primarily interested in the California smog/emissions test format.
And, I am mostly interested in the 1st generation Lexus V8 of the 1990's (LS400, SC400), otherwise, the comparisons are not very meaningful.
Hopefully, if we get enough posts, we can see the range of emissions, both high and low.

1992 SC400:

2001 / 70K miles / 25 MPH results:
15.2 %CO2
0 %O2
4 HC PPM
0 %CO
215 NO PPM

2003 / 84K miles / 25 MPH results:
15.4 %CO2
0 %O2
12 HC PPM
.01 %CO
25 NO PPM

2005 / 90K miles / 25 MPH results:
14.9 %CO2
0 %O2
1 HC PPM
0 %CO
105 NO PPM

2007 / 98K miles / 25 MPH results:
14.9 %CO2
0 %O2
7 HC PPM
0 %CO
275 NO PPM

2009 / 138K miles / 25 MPH results:
15.0 %CO2
0 %O2
19 HC PPM
0.06 %CO
236 NO PPM

New distributor caps/rotors installed 2010

2011 / 161K miles / 25 MPH results:
15.2 %CO2
0 %O2
7 HC PPM
0.03 %CO
253 NO PPM

2013 / 165K miles / 25 MPH results:
15.0 %CO2
0.1 %O2
23 HC PPM
0.07 %CO
247 NO PPM

2015 / 171K miles / 25 MPH results:
14.8 %CO2
0.0 %O2
25 HC PPM
0.10 %CO
295 NO PPM

2017 / 173K miles / 25 MPH results:
14.7 %CO2
0.0 %O2
27 HC PPM
0.13 %CO
282 NO PPM

New ECU installed

2019 / 175K miles / 25 MPH results:
15.5 %CO2
0.0 %O2
22 HC PPM
0.07 %CO
245 NO PPM

2021 / 176K miles / 25 MPH results:
15.3 %CO2
0.0 %O2
11 HC PPM
0.05 %CO
300 NO PPM

2023 / 176K (sic) miles / 25 MPH results:
14.9 %CO2
0.2 %O2
79 HC PPM <--failed - max allowed is 56
0.18 %CO
538 NO PPM <--failed - max allowed is 487

This is for a SC400 with minimal ignition/fuel/exhaust work (except as noted) since I bought it in 1997 with 45K miles.
All emissions remained low, even as the miles piled up, until my first failed test in May 2023. There's a quite a rattle coming from the cats upon start up, so I'm guessing it's time for a new cat or two. Will update this once I have it looked at.
I would have expected all levels to slowly rise over the years, but that's not usually the case.
I'm more inclined to blame variations in the fuel, testing equipment and engine temperature when tested than variations in the engine's emissions/ignition/fuel system.

 

93 sc400, bone stock

I don't have a current copy of my readings, but the one I do remember is the HC... my car was the cleanest we ever tested on our smog machine for at least the past year, maybe more - except Nevada does idle and 2500 rpm tests...

the car was around 180K when done, idle - 2 ppm HC, 2500 rpm - 1 ppm HC...

Not sure how Californias systems are checked, but out smog machine is calibrated monthly, and in discussion with the guys, they almost never have to change anything, just run the test to make sure it's within specs...

 

my last check was

15mph test 1555rpm
14.6% C02
0.0% 02
7 PPM HC
0.01% CO
24 PPM NO

25mph test 1602rpm
14.6% CO2
0.0% O2
3 PPM HC
0.01% CO
35 PPM NO

I have just BFI cone filter setup and a JIC catback.

 

Recently, an owner of 1900 LS400 w/120K miles posted his smog results from 2015:



Way lower in the HC and CO, but a bit higher in the NO dept.
In fact, it only went up from there - you can read more about his struggles with the CA smog test at his thread here:
https://www.clublexus.com/forums/ls-...les-1uzfe.html

 

That's quite a thread bump.
Ours from 2018 at 203K
Freshened vacuum lines, PCV valve, O2 sensors among various other sensors that were replaced at earlier miles. The Electronic Coolant Temp sensor is a big factor in this too. To bad he didn't check back in that thread.