jac, ugpm
for A/F ratio, wideband sure better than narrow band which directly get the info from o2 sensor
for wideband, the o2 sensor has its life spam like 500hr? not sure bout this tho
boost: to monitor yr intake pressure, the air flow stability, prevent overboost by monitoring
ext temp: engine kaboom(blown) o not depends on this info, u wont wan yr engine to stay 500'c during idling o over 1000'c when boosting
a/f: more fuel > more carbon > less power > lower temp
less fuel > less carbon > more power?(not sure bout this) > higher temp
oil temp: like tofuman said, more power > heat, the higher temp for yr oil temp, it actually cooks yr oil which u decrease the life spam of yr oil(assuming there is life for oil, who knows?), additional oil cooler can lower yr temp, increase yr oil's durability, bad thing is, some claim additional oil cooler can lower yr oil pressure
oil press: leave to the pros to explain as i'm not too sure bout this