Thanks guys.
I have swap around the coil and plugs.
I believe we checked the injectors, but need to check the electrical connector of the coil pack.

Nepolian,
We did this test...
we put the car in idle, and then try to pull out the coil from cylinder no 1 and the engine seemed about to die. Now, coil 2 and 4 all have same symptoms. Now cyl no 3, no after effect at all.