I have a SPD Dyno Dash, in the menus i can make a screen to show me various things like water temp, voltage ect... There are also two choices for Boost and the other for Air temperature. Does any one know where these two sensors are taking their info from? How accurate do you think they are?

FYI Just idling the boost shows ~ -10 and the air temp shows about 125.

Since this is posted in the 1st Gen forum...I will guess that you are referring to the R53.

If that's the case...there are two MAP sensors, one bolted right on the front of the intake manifold that reads both air temp and pressure, and one on the drivers' side of the cylinder head above the thermostat housing that is plumbed in before the SC and only reads vacuum.

Yes its an R53. So if im reading the temp and pressure from the intake manifold, is this going to be different then if i installed a boost gauge? I guess what im asking is, is there a point to a boost gauge if i can use this sensor with my device, or is a boost gauge going to be different information?

what the T-map sees will be pretty close. The boost is typically gotten from the sensor on the intake manifold, where the IATs are measured as well.

Also, the OBD-II on the R53 is pretty slow (2-3 Hz) so peaks may not show up quite the same as a dedicated gauge that doesn't have these sampling issues. Also, I think the sensor reports absolute pressure, so your gauge may be doing something to correct for ambient. If it's just subtracting 14.7 (atmospheric pressure at sea level) you may get offsets of a couple of tenths as well. I'm not sure, but I don't think the car has a barometric pressure sensor to do real time corrections. Some fancy boost gauges measure this before the car is started to get the local correction, FWIW.

Matt