Hesitation @ ~2800 rpm

[pf55112]

On my '99 Miata. It's worse when cold and damp. I've replaced plugs and wires but neither had any effect. It's almost unnoticable in the summer...Any ideas on what else to check?

 

[JDM-P5]

I'm assuming it's not turbo'd or supercharged. You need to be more specific.
However, if it does this only in the cold periods of the year, it's probably just the infamous stutter in the cold. Keep an eye on it, but if you don't notice it in the warmer months, it's not serious.