2003 Mitsubishi Galant Rough idle/ hesitation

I have 2003 galant it recently began to hesitate when I t depress on the accelerator. If I let off the gas & gradually press it down it will smooth out. I can stay at a steady speed with no problem. Once I decelerate, the hesitation will come back when I press the accelerator again.
When at idle in drive, it will sometimes idle at around 500rpms.

I have changed the plugs, coil, valve cover gasket & spark plug gaskets.
When hooked up to the code reader, I reads misfire in cylinder 2.
What else could it be