First of all yes fix that header leak, it will leak boost and cause sluggish spool.
Is your coolant temp sensor (ect or cts) unplugged? mine read negative when i forgot to hook it up. L8 is LV8 the engine load variable, basically a measure of engine load that is calculated from a formula based on maf reading, rpm, and a few other things that i don't recall. AF is airflow, same as mass air flow. they are just the truncated versions to fit on the scanmaster screen. make sure to take the readings at a warm idle in park. CC stands for cross counts, which is a countdown of how many times the O2 sensor reads rich to lean or lean to rich. It should cycle from 0 to 255 in a certain time frame, i believe a minute or so, which means that the sensor is good and active. Please note that it will jump up by several numbers at a time because the scanmaster can't update fast enough to show every change, and it would be hard to watch anyway. the two main numbers are indeed 02 sensor millivolts, they should read 780-800s or so at wide open throttle. the number next to the o2 (0.0) is the number of degrees of timing that the computer retarded the timing because it sensed knock. This should be zero or maybe a degree for false knock on the shift.
BLM and INT are your long and short term fuel corrections, respectively. The computer tries to keep a moving average air fuel ratio of stoich most of the time during normal driving. The integrator (INT) happens every few milliseconds, the (BLM) block learn multiplier is the long term correction which is essentially an average of the INT and happens only like a few times a second. There is a much better explanation on gnttype.org I believe . Pay attention to the BLM, the int doesn't matter all that much for everyday stuff. BLM ideally should be 128 at a warm idle and so should INT. High BLM's at idle indicate vacuum/ exhaust leaks. Maf reading should be about 4-6 (this is grams per second). There is some other stuff like IAC but I am out of time. A search for something like scanmaster numbers will find you what you are looking for before I can reply again. Also I believe the bulk of the info is on here or gnttype. good night.
oh well. Part # at A.Z. is SU109. Doesnt cost much and GM used/uses it on almost everything since mid 80's.
My 87 wouldn't start with it disconnected but you never know, some might I guess. Until figure out why it's in the negatives your car will never go into open loop.
