Muggy high humidity days significantly improves performance - But how?

[BennVenn]

i'm not sure a log will tell you if your timing is out, or how much torque you're making, or even how much air is being ingested (assuming map sensor). Both logs will look identical, perhaps a touch richer on the humid days. The only difference would be on the dyno. Or take a few degrees out on a normal cooler day and see how it drives?

[vlad01]

I wonder if your timing is too far advanced, and the humidity plus reduced oxygen is bringing your timing closer to optimal?

Perfectly valid logic which I also glanced over but since they have been tuned on the dyno, they are on the optimal timing. VR MBT at WOT peaks at 27, nearly 28 deg with 9:1 comp and VN-VP with 8.5 comp like 29 deg.

As I tuned them, I found that power barely changes from from 27 to about 32 on a VR engine where either side starts to fall outside of run to run variance, the boost in performance I am feeling feels like going from a stock memcal to a proper dyno tune once you have installed headers kind of gain, like maybe 10hp?