fix a misfire on a citroen saxo furio 1.4?

Car will run find and randomly start misfiring. More when you come to a halt. You will try to pull of and the engine will cut out. Then when you start it up it will take about 20 seconds to get going. It will then be misfiring and you have to rev it to get it firing correctly again. There is a smell of petrol afterwards. I have replaced the coil pack and the problem is 99% better. But it has still done it twice. When i replaced the coil pack it was spitting raing slightly. Does any think this could be causing it? maybe a bit of rain got down where the coil pack goes? Also should i replace the plugs?