It came in the mail yesterday, so I got to mess around with it with an air compressor. I tested at each pressure a bunch of times and it was never exact, but stayed within an ohm or two every time.
To sum it up: it's probably the most accurate aftermarket option we have. 0, 1/4, 1/2, 3/4, and full are as close as we could hope, so it looks like NOS isn't the only option anymore, if you want an accurate reading.
0 psi: it was slightly different every time I brought it back down, but 4 out of 5 times it was between ~72-74 ohms, once it stayed around 68-69 for some reason, but even that would basically not register on the gauge.
28-30 psi: I was able to get around 23 ohms (1/2 reading on the gauge). That's very close to what it should be because if you look at the gauge, 40 psi isn't actually halfway.
80 psi: Almost exactly 10 ohms every time
These 3 are basically perfectly in spec, which is better than any aftermarket stuff that I know of.
I also messed around more to see if the rest of the sweep was correct. Based on other tests I've done with new OER gauges, 1/4 full is about 37-39 ohms and 3/4 is 15-17 ohms. I was able to get 39-40ish ohms somewhere between 10-15 psi and about 16-16.5 ohms at 55 psi. Again, basically exactly what you'd expect by just looking at the gauge.
You can also use this sender and those 5 data points with an air compressor to test your fuel and temp gauges. If they're far off, the gauge is the issue and needs to be adjusted. If not, then the sending unit is. For fuel, 9/10 times it's the aftermarket sending unit and a Metermatch is your best bet.
Just to mess around more, I checked at each gauge marking (20, 40, 60 psi), then tested everything hooked up to an untouched new OER gauge. Ohm readings are below but, on the gauge, everything, including 0 and 80 psi, lined up very close to the correct markings.
20 psi: 30-32 ohms
40 psi: 19-20 ohms
60 psi: 16.5-17 ohms
This also confirmed for me that I (and everyone else) should use the other port on the block, or a tee, and put in a warning light. When I dropped pressure down to 0, it took about 15-20 seconds for the gauge to catch up and read correctly. Add this to however long it would take you to notice, and your motor's toast by the time you shut it down.
