Gunson gastester question

[Platiporsch]

1980 SC, oxy sensor disconnected,calibrated to 2.0%,engine warmed up,inserted probe into side port of cat and got a reading of between .2%and 1.8%. That is way to lean correct.am i not looking for 4%-8% according to Bently.

[pbs911]

8% is to high for the CIS. John Walker has posted several times that the SC likes the CO at about 3.5 - 4% at 35 degrees total advance. It actually sounds like the readings you are getting are in lines with smog regulations, at least that is where I set mine for emissions testing. I can never remember whether you disconnect the O2 sensor for the reading.

[grant lyon]

belt off, or air inj line plugged?

[Jadams1]

I was curious, how much do those testers cost ? How do the results compare with those obtained from an official sniff tester?