Okay I've read as much of the threads I could, but I guess the relationship between air-flow, fuel, co2 adjustment and surging is not completely clear to my uneducated brain.

As I understand, this bike runs lean, but also needs more air. More air results in an even leaner bike, so the CO must be adjusted up to increase fuel richness. CO up = richer fuel = good.
The surging is related to this lean/rich/better air-flow equation.

What I want to achieve is more power in the lower gears at lower revs - the gap between 2nd and third is sometimes inconvenient, 2nd being quick to rev too high and 3rd not having enough revs to take over the job.
I'm not really interested in top-end gain.

Here's what I am doing - I have removed the snorkel and intend to drill two holes in the sides, and install a dna filter.

The response seems better for the snorkel removal, but the CO adjustment is a much more elusive trick to master.

So far I have increased Co from 5 to 13. I still experience a snatchiness in certain rev ranges, though I'm still not sure if it's an improvement or the same as it was. Given I've increased my air flow slightly, doesn't that mean my air/fuel mixture is more or less as it was before?

Will adjusting UP, in theory, decrease my surging? Can *overadjusting * the co increase the surging? How do I best find the sweet spot? I had it at 20 (15 above) and it seemed snatchier, but maybe I was imagining it.

When I do install the new dna filter and/or increase the air flow with holes, will I need to adjust up again or should I leave it?
How will I know if the bike is too lean?

Why does increasing the airflow past a certain point (stage 2) make the co adjustment no longer effective and I then need a fuel mod?
Why does the co adjustment not compensate for the extra air flow -
and isn't that what an EFI system should do automatically anyway?

If I do get a fuel mod, will I need to put the co back to what it was otherwise it will be over-rich?

It's a bit annoying it doesn't do these things automatically and has to be tricked into doing what we want it to.