Re: 156 engine misfiring?
Dunno if the 1.6 is like the 1.8 in the ignition department but my wife's did that a while back. On taking it to bits I found three things:
1. Whenever the oil gets topped up, if any of it spills into the recess round the oil filler cap, it trickles down the side of No. 1 plug.
2. On the Twinspark, one coil tower goes straight on top of one plug and then there is a long shroud that goes over the other one. The insides of the rubber shrouds need to be PERFECTLY clean or there is a chance they won't seal properly against the porcelain of the plugs and will track.
3. When I pulled the long shrouds off the coils, three of them were just full of powdery green verdigris. The brass connectors inside had just turned to powder.
4. On three of the 4 coils, there were small cracks in the plastic housings - just near the split line where they are moulded. Although I couldn't see any evidence of tracking, I epoxied the cracks up with Araldite.
Hopefully, some of those might help!