2001 1.8T 77K mi
Symptom is rough idle and missing when cold with codes 301-5 – all 4 cylinders. And cold means leave it overnight cold. Once it’s warmed up drivability is great and it doesn’t give any codes.

I’ve replaced: plugs, coilpacks, melted check valve, split vacuum hose, and air filter with only slight improvement.

If I disconnect the MAF when it’s cold it idles much better and just throws a MAF code. Drove it a shot distance with the MAF disconnected and it didn’t feel like it hesitated but it threw some misfire codes. Is that normal? Disassembled the MAF and cleaned it very carefully using instructions here. That made it worse and not really drivable when cold but it still runs perfectly when warm.

I’m about to buy a new MAF at stealer prices because we need the car running. If that doesn’t fix it I’m out of ideas