I have a question about A/F readings and a cam

Calibration is most likely, then. What kind of gauge do you use? Some seem to have a reputation of not holding a calibration.

If all the signs check out though, run it! There's plenty of things that could throw off the lambda reading, like burning oil or contamination of some sort on the sensor, or even that you have one or more cylinders that are leaner than the average - meaning that the aggregate mixture needs to be richer to make up for the few lean cylinders. Personally, I'd grab an IR thermometer and check the collector or manifold runners and see if there's any major imbalance just to make sure. Could be something to do with the carb and not feeding both side equally (do you have a single or dual plane intake?).

Metering rod springs could be worth a check, but if you can kill it with the idle mix screws then they're probably not a major culprit. They're easy enough to swap though that I'd do it anyway to see if there's a difference.