This is a good point too. I'm not entirely clear on
the true nature of oxygen sensor electrochemistry
but if you are getting shoot-through (like from a
strong scavenging vacuum bounce and a high
valve overlap cam) your exhaust will contain a
high oxygen (and fuel) level. Everything I've read
indicates the sensor works off exhaust gas oxygen
partial pressure and this sort of "assumes" fully
combusted air/fuel beforehand (for the 14.7:1 = 0.5V
ideal output notion). If the air/fuel >exhaust gas is
not burnt then you could be indicating the oxygen-
based (false) voltage and not the eventual (burned
down by the cats) true chemical balance like will
be seen by a downstream wideband.
Originally Posted by MyLS1Hauls
LTs can actually over-scavenge the cylinders at low engine speed and can actually pull air/fuel right out of the motor and out the exhaust. I still get 20mpg average with all of my mods and a stock target a/f ratio. Remember though, stock o2 sensors are only accurate at 14.7:1 so I'm not sure how well changing the target will work. Worth a shot though.