Scott and Trendsetter,
Thanks! I figured the map might be missing a legend or something but not knowing how to read the thing in the first place, I couldn't be sure. I got your email and those articles are very useful. I clearly have quite a bit of study to do.
The link above is also full of information.
Is there a way to calculate how compressor efficiency (and maps) may be affected (shifted) as a result of other restrictions in airflow (manifolds, restrictor plates etc) or does efficiency of the unit remain constant and engine power and torque values simply shift dependent upon the changes in airflow?