if its a coil pack issue you can,check it with it running. Just pop a ht lead off one at a time to see if there's a spark firing. Its most likely an injector failing. Just swap it round with another and see if the fault moves with it. As for where to buy its the usual ecp of gsf. There's a discount code thread on here for both as they run promotions most weekends. Ngk for sparks nothing else. Oe Renault for leads most recommend.So, last month I had a misfire. Changed the pre cat lamda as per the scan. now its got a misfire on cycinder three. I'm going to go for coil pack and all plugs. just after advice where I should buy. Obviously best quality, cheapest price.