You can drive without the flap and put the unit back in place to seal the hole up. The SES light will come back on though within a short amount of time. The engine will continue to misfire and idle poorly until you replace it. The car will always appear normal once you clear the codes, but will progressively get worse and even possibly stall out on the road.

DISA = Dual Resonance Intake System. It is a butterfly system that switches to allow airflow from longer to shorter intake path's in the manifold.

Longer = better low end torque
Shorter = more high end H.P.