Recently I've been getting heavy misfires under load. Engine light flashed, then stayed on. I knew the coils were old so yesterday I replaced all 4 with new R8 coils sourced from AKS. I got the car scanned and cleared the fault codes:
Took it for a good blast and it all seemed fine. Yet today, the misfire is back. Under load, coming onto boost, and it bucks and splutters with big pops out of the exhaust.
Now I'm thinking it can't be plugs, as these were new 2k ago, fitted at Statller.
One thing I have noticed recently is a slight metallic 'rattle' or 'tinkling' with a cold engine coming onto boost - obviously on very light throttle and changing up at 2200rpm or so. I'm very careful to treat it sympathetically when it's warming up. I don't hear this noise when it's up to temp.
Reading up on this led me to the theory of a loose wastegate. So, is there a chance I have a dodgy N75, considering it shudders and misfires just as boost is building? The misfire specifically on cyl 2 tells me it's not, but I'm not ruling anything out.
Steve's working on his race engines this month so I doubt I'll be able to get it in to him any time soon.
Any ideas?