Make sure your idle is close to 900rpms, as well as checking the other stuff.
Yes, it can cause that if there is a leak. The throttle plate is closed, and the vacuum in the manifold is as high as it will get then. It only gets greater, when you close the throttle and use the motor to slow the bike down. That causes the vacuum to spike enough to pull extra fuel through the Coasting Enricher circuit.
If the exhaust gaskets are leaking, it introduces oxygen into the pipes right at the head, and the fresh air can combust any unburned fuel in the exhaust. Which is how the AIS
works, when it is still installed on the bike.