Missfire help

[greenmachine]

Well got back from work this afternoon, car was running fine, went to start it up tonight to go to the over halfs, and it was missfiring slightly, i thought it would just be one of the coils being damp, so proceeded to drive it down the motorway at around 60 in 5th around 2500-3000 revs it didnt seem to missfire or lose power, so when i turned off the motorway onto the slip road it was getting worse, parked it up with it sounding rough as hell, came back out, and its even worse, drove home and it gradually got better, only missing and losing power when accelerating hard, what the hell is wrong with it?

i know from previuos experience when washing it with a hose how it didnt like water much and missfired then (my first time out driving by myself after passing my test that morning) but it sorted itself out after idleing until up to temperature.

ive seen on variuos threads on the web that its a common fault with the renualt scenic for coil packs to go.

any help or advice would be appreciated cheers Greenmachine.