Now that I've fitted a Scangauge, I'd like to know how to make the best use of the gauge readings to determine whether there is a problem.

VLT (Battery Voltage)

The User Manual is pretty clear on this one:
WT (Water Temperature)

Again from the Users Manual:
What coolant temp should you see cruising at highway speeds?

MAP (Manifold Absolute Pressure)

I know the reading has to be adjusted by subtracting air pressure relative to altitude to determine boost. Do you correlate this reading to TPS (Throttle Position Setting) or LOD (Engine Load) or some other reading to determine if you have a boost leak?

IGN (Ignition Timing)

Anything to watch for here?

 

Regarding water temp, depending on the weather, I get highway temps between 185 - 211. The highest reading I have gotten so far, in creeping traffic at 95 degrees, 85% humidity, 225.

 

Well, I can only answer one of those: at cruising, your water temp should read ~190F. That is, unless you have switched to a different temp thermostat.
BTW, thanks for the link to the pressure chart! I knew mine was lower here (5000 ft) but had no idea that it was 2.5PSI !

 

Here's my recomendation.

I would idle your car and see what temp the fan kicks on. That would be as close to as max temp as I would want to get regardless of what the manual says the boil temp is.

Highway speed is 190 or less like previously noted.

Timing? What info are you going to get from monitoring this? Since this is computer controlled and I'm not sure what the measurement is on the gauge it is somewhat meaningless unless you are curious to know when you are advancing and retarding timing. Again you would probably have to watch this. I think as RPM's increase timing is advanced.

I don't and wouldn't want to calculate what the guage boost reading is - altitude = boost everytime I looked at it.
Comparing to Throttle Position and Engine Load would be pretty hard to do since the sampling rate of the gauge is pretty slow? I suppose if you were cruising down the highway you could have those 3 on the gauge and monitor then to see what you are getting.

If you have a boost leak it would be very apparent IMO and you would have your check engine light on, hear it, feel it in reduced engine performance.

Main ones to watch imo are Water temp, Volts. I have the MAP on mine just cause I like to see what it does.

If I wanted accurate boost readings realtime I would install a guage that is dedicated to that.

 

I know on some forums I've seen "sticky threads" where people have entered specific data from the ScanGauge in an attempt to determine some real world averages. Might be something to request here if there are more than a few people running a ScanGauge.

Oh and a group buy would sure be nice!