Is 'Air gap' for Auto sampler analysis and carrier gas flow rate can reduce the Peak area?

The airgap is the amount of air that will be behind the sample in your syringe. So if you have 0 airgap in your syringe, it means that the plunger is directly onto the sample. If you have lower area, it is a possibility that there is still some sample in the syringe that has not come out and that is why you are seeing what you are seeing.

Also the fact you have different flow rates make me think your peak shape is not identical which can be a difference in the integration of the peak as well.

The airgap is the amount of air that will be behind the sample in your syringe. So if you have 0 airgap in your syringe, it means that the plunger is directly onto the sample. If you have lower area, it is a possibility that there is still some sample in the syringe that has not come out and that is why you are seeing what you are seeing.

Also the fact you have different flow rates make me think your peak shape is not identical which can be a difference in the integration of the peak as well.