Fuel level should barely trickle out of the plug holes with the plug out, sounds like they are too high. Doesn't explain your problem though, which is strange. Plugs don't explain it, nor does fuel pressure as it should be the same day or night. I run a 750 on my Air Gap but I run thru a cool can so fuel is always the same temp an no problems. Your issue sounds like it may be humidity related. Tune your carb with a vac gauge attached to the manifold. Adjust the mix screws until you obtain the highest vac rating at idle. Beyond that I have no other ideas to offer for this weird issue. Most engines run better in cooler air.