You can weld in the O2 bung on the exhaust pipe using any mig welder or little 75amp 110v stick welder
YOURSELF. You can even read the (heated) NB O2 sensor using a DVOM.
You can test/restrict the PCV valve air flow YOURSELF. pinch the hose.
If the resulting change helps, just find a PCV valve with less flow at idle.
Hold the engine rpm at the rpm point above idle that you want to investigate.
say 1500-2000-2500 rpm Now pinch-restrict the PCV hose with pliers while watching the Voltmeter/AFR gauge
for the crossover voltage point .450MV rich/lean +/- crossover point.
This will show you how close you are to 14.7:1 AFR.
A NB is very accurate at showing the 14.7:1 cross point. And manipulating the PCV air flow by hand while watching the gauge will show you where you are at.at various above idle rpm/throttle points.. Thats what you need to know.
is it richer than or leaner than//.Stoichiometric....?
You do not need to know the exact AFR. Off idle transition AFR leaner than say 15.5 is too lean (drivability)
richer than 12.8:1 is too rich.
Just get it close to 14.7:1. There is no ideal ratio. close to 14.7:1 is good enough thru the idle transition.
But first set the curb idle for best idle using a vacuum gauge and get the throttles position correct.
The AFR gauge will be richer than 14.7:1 at idle, when the idle is set correctly.
Play with the pri and sec throttles idle position and idle base timing .
You don't need a wide band for any of this tuning.
Same with WOT power main jet tuning. You don;t need to know the exact AFR.
You just need to know if the jet change you just made up or down in jet size made you go faster or slower.
and wether your jet changes are getting you way too lean @ WOT.
Less than .800MV @ WOT on the NB voltage. It works as a (you are way too friggin lean
) warning device very well Once you learn how to use it..