Plus you indicate you have a manometer but don't trust it, why? Without a reliable draft gauge you have no idea what the draft is.
Mainly because the readings have been all over the place.
Even with clean probes.
I have zero set it quite often.
Recently, after brushing my chimney and cleaning my pipes and with fire full blast on a cool day with everything open, it barely reaches .10.
Now, after a quick and dirty pipe and chimney clean, it barely reaches .08 in the same circumstances.
I also blew out the probe with compressed air.
I, recently, put a new probe and hose on. I THINK
the probe is pointing away from the furnace towards the chimney.
Maybe I should restate that.
I'm sure the probe is pointing that way but not sure if it's pointed parallel to the pipes or tilted down or up; if that makes a difference.
After the new probe was installed was when I noticed the mano moves very little.
Either it was wrong before and right now or it's wrong now.
To use your words, I don't know if it is a reliable draft gauge.
Because I'm not a very bright man, I ask dumb questions.
Before, everyone had manometers, how did they tell if they had a reliable draft?
Same thing could be asked about the CO detectors.
I am going to get some more CO detectors and use them in conjunction with my present ones.
If some of them alarm, how do I know which is correct?
In all cases I will err on the side of caution and run like a chicken with my head cut off if one alerts.