I chose this one because Standard Motor Products has a reputation, and I wanted to be sure it would work. I was disappointed.I was afraid I'd been sent the wrong item because the box said it was an engine control unit and had instructions for installing one. The end of the box had a Standard Motor Products sticker with a red border, saying it was an MF20006. Beside it was a sticker with a blue border and a bar code, saying it was made in Mexico. On the item was another sticker with a blue border, labeling it as an MF20006S. The S made me uneasy because I didn't know if the specs were different.Nissan's shop manual gives resistance readings to check the mass airflow sensor. The figures are inadequate to show a sensor works correctly, but they were all I had. When I tried to check with an ohmmeter, I couldn't get readings because the contacts in the connecter had a hard gray coating. It wasn't like any copper corrosion I'd seen. I worked on it with sandpaper and a jewelers screwdriver.The original had a square rubber gasket similar to an o-ring. The remanufactured one had a cardboard gasket, instead. I reused the old rubber gasket because it would be more foolproof. It made me uneasy that Standard Motor Products hadn't procured the proper five-cent gaskets.At 2000 RPM I heard pinging and afterfiring. I couldn't keep the engine running any slower. It was as if I had a big air leak, but I couldn't find one.The vendor, autoplicity, treated me pretty well. I was afraid it would take a long time to arrive because they didn't offer shipping options or estimated times. It arrived quickly. When I said I couldn't get it to work, they quickly authorized a complete refund. They even emailed me to apologize!I bought another, much cheaper, rebuilt unit, and the engine ran fine.On their website, Standard Motor Products mentions only their manufacture of new parts. I don't know if what I received is typical of their remanufactured stuff.