Measuring around

If you remember, in a previous episode I found the exhaust connection past the turbo elbow was leaking. So, I decided to unbolt it and take a better look. As I removed the first lock nut, I noticed the stud had seen better days:
I think I will see if I can run a M8x1.25 die in each stud to be on the safe side. I will also replace the nuts with stainless steel ones and lock washers. Probably that is about as heat resistant as the factory ones but at least they would be clean. In any case, After a bit of persuasion, I took out all nuts and dropped the collar holding the studs.
If we look under the elbow, we see the connection is a conical one: the downpipe is press fitted over the turbo elbow by the collar with the 3 studs. So, no gasket is required here.
Underneath the elbow is the oxygen sensor.and on the top is boss that could be used to, say put a wideband sensor or EGT probe. Hmm, ideas .Time to do some measurements: first we have the temperature sensor used by the ECU. I was told at SaabCentral that it is between cylinders 2 and 3. Another way to find it is the connector that goes to it: it is blue.I unplugged the connector and found its pins were rather filthy. I do not know if they are corroded or just covered with some hardened goo.One way to see if the sensor is working is to test its resistance. You see, the temperature sensor is a thermistor: as temperature changes it changes its resistance. In fact, as temperature increases it decreases its resistance: 2600 ohms @ 68F and 320 ohms @ 176F +/- 10%. I measured 1720 Ohm, which should be close enough (it was more like 80F).The we have the temperature sending unit used by the temperature gauge, which for some reason is not moving. So, I thought on starting by checking if the sending unit was working. As before, the best way is to measure its resistance. According to my multimeter, it is 440 Ohms at the same temperature as before. Is that right? I don't know because I do not know if the curve is linear or not; the only other data point I have is 51.2 Ohms +/- 4.3 @ 194F. I guess that is consistent with my expectations: the resistance to drop as temperature rises. Still, I would love to get more data points or a plot of the curve. At least I am not getting an open or infinity...
In any case, that is how far I went today on the Saab.