It couldn't be vacuum related. Test the component, I'm not sure how you would do that though. Maybe test the resistance of it to see if it's within spec.

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1990 190E 3.0L

another user PM'd me some great info. It turns out the California emissions cars use different diagnostic codes than the non Cali cars.

most of the codes are the same, but the pin 8 is different.

8-4 is a MAF code
8-13 is an o2 sensor code.

Maf's are cheap.

I think my plan of action is clean the maf, clean the IACV, test the voltage for the o2 sensor, do a static discharge and go from there.

Though the more I stare at those codes, and the more I read, I'm guessing I'll be doing intake manifold gaskets shortly. My inner mechanic says go with your gut of vacuum leak.