Mine's been doing that just recently (past few weeks), first chance I had to look at it was last week (don't use the car much) & quickly saw that the HT leads were looking decidedly second-hand & there was a mark on the underside of the bonnet where lead#3 was rubbing. Changed the HT leads & when removing them found that one of the connectors at the dizzy cap had broken, the misfire, slight smell of fuel & general sluggishnes at low revs are all gone.
When ordering the HT leads Andy at Promax suggested it could also have been the throttle position sensor, and from previous experience I know dodgy connections to the AFM can cause the same problem.
Give the car a service as Paul suggests & see if that improves the problem or cures it as it did with mine.
