Failed CA smog. Need advice

[bmwvsevo]

Hey guys.
My 99 M3 project car failed CA smog test today. I am attaching the pic of the values. Only "NO" parameters barely failed, all else passed. Max 430- mine 554 (at 15mph)
No CEL's on the dash. Smooth idle. Any advice guys how to pass this painlessly?

I did some research and found out that there are few possible reasons:
1. Cooling/overheating- I have just redid all the cooling including 80' Thermostat, Stewart pump, new radiator etc. Stock Temp gauge sits dead middle.
2. Bad gas maybe- since I got the car as a project it still has the same over half tank of unknown gas. So this is a possibility.
3. Bad cats. The smog tech stated that one of my cats is a replacement. Possibility also.
4. Could O2 sensors be bad?

Do the spark plugs play a role here? I havent replaced them yet. I do have a new set going in though.
Also, my buddy has OBD1 m3 exhaust but it has 1 O2 sensor, is there any way I could use his exhaust without welding a bung on?

Thanks in advance guys
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[Korath]

1. The cooling system probably isn't the issue here. What has been done to the head? Mileage on the drivetrain?
2. Get that gas out of there and go fill up with some 76.
3. A bad cat also causes your HC to creep up to the limit as well.
4. Having just high NO is usually an indicator of running lean, so definitely check those o2 sensors.

That's just the little bit that I've figured out with my M3.

[bmwvsevo]

1. The cooling system probably isn't the issue here. What has been done to the head? Mileage on the drivetrain?
2. Get that gas out of there and go fill up with some 76.
3. A bad cat also causes your HC to creep up to the limit as well.
4. Having just high NO is usually an indicator of running lean, so definitely check those o2 sensors.

That's just the little bit that I've figured out with my M3.

Forgot to mention that the mileage is 230K. There was nothing done to the head as far as I know

[bmwvsevo]

Ive ordered 2 o2 sensors.
Any other suggestions guys?

[Korath]

If you were really close, you could try half a tank of gas and add a gallon of denatured alcohol. That will clean it up just enough to pass, and then you could tackle the diagnostics.