Hi There,
It has been more than five years or so since I last flew into Manado, but between the periods of 2004-2006 I frequently flew into manado.
At this time of year, haze would not be your primary concern, I would worry more about heavy rain, as there is so little or no wind, so the rain could stay there for a while. Manado is also a non radar environment, and is very busy in terms of traffic. Most of the time, even up to 10kts tailwind, RWY36 is in use, and the instrument approach available is mostly the above mentioned NDB, the ILS 36 used to be always notammed as Not Calibrated although they keep it on air.
Hope this helps
SS