hey folks, thank you so much for ur replies.
I decided to check one by one. So the 1st thing to do is to clean ICV.
i've check the connection and cleaned it by elec part cleaner.
However, is there any way to clean the valve without removal of manifold?
I think I gotta replace ICV if cleaning doesn't work.
There are over hundreds of posts regarding this, but i've never seen
any 'how to' with pic for m50's ICV.
thnx