Failed Emissions... AGAIN

[AndrewBird]

First off, this in in my M50 powered E34.

Trying to get my car to pass DEQ. Failed first try, then did the following and failed again:

Replaced O2 sensor
Replaced cam position sensor
Replaced VANOS solenoid

^^^ These three thought I had it fixed as the car runs much better now and I gain 4mpg.

Checked coolant temp sensor - Good
Check air intake temp sensor - Good
Check throttle position sensor - Good
Check wiring from all sensors to ECU
Swapped out MAF for a junkyard one - No change
Cleaned MAF, both original and junkyard one
Checked fuel pressure at the rail - Good while engine off and running
Replaced coils
Replaced spark plugs

Recently I've also:
Had injectors cleaned and flow tested - 1.5 years ago
Replaced fuel pressure regulator - 1.5 years ago
Replaced fuel pump and filter - 3ish years ago
Rebuilt Vanos - 6 months ago

I'm running out of ideas. I'm thinking I'll get it smoke tested to verify no vacuum leaks, though I don't think there are any. Only other thing I can think of is bad cat perhaps?

[squidmaster]

What are you running for a cat?

[AndrewBird]

Stock.

[squidmaster]

The high hydrocarbon is unburned fuel. This can be caused by any number of issues. Do the smoke test and check spark plugs (seeing what color the tips are should help find any issue areas)

[LJ851]

I bet it would pass with a new cat. I have put a few cats on my car over the years and when they fail (for me) it showed up as high HC every time.

[AndrewBird]

Looked up the cat. It's specific to E34iX, I'm guessing due to how it fits around the transfer case. Schmiedmann lists it, but it's $1500+shipping from Denmark!!!

My valve cover gasket is leaking a bit, so I think I will start there.

[nrubenstein]

If they aren't testing for NOx, put a ton of E85 in.

[Kershaw]

An exhaust shop can put in a generic cat.