you cant safely monitor your afr's with the factory o2 sensor,
you have to buy a wideband ego
either the...
SM-AFR from
http://www.plxdevices.com/
or
LC1 from
http://www.innovatemotorsports.com/
dont expect much/any change from $450 if you get the kit inclucing the gauge
personally I've just sold my lc1... lost faith in there product after having one die,
and there sensitivity to earthing, and poor quality control and slow RMA
I'm now saving for the PLX unit
to be honest i woundnt worry about upping the boost a bit,
if your really paranoid.... a Dyno run with AFR check will set you back aroung $80?