Back to square 1

I started the car to warm it up this morning and it started fine, idle was perfect and it reved completly fine. i went back inside and every so often i could hear the revs go up and down for a few seconds, happened twice over about 20minutes. when i got in the car and drove to work all felt great as it should pulled well didnt stutter or miss untill i was sitting at a set of traffic lights, the idle begain to die and it was missfireing when i tried to pull away at low revs it almost stalled and when i dipped the clutch to rev it, it reved perfectly but i wheelspinned like a B**** then it was fine again all the way to work. last night it was running badly and i suspected it was because of the rain so i changed the coil, the dizzy cap the rotor arm and the HT leads, it didnt do it again last night, but the rain had stopped.............
and it was fog this morning.