I was just browsing the threads and came across this one. So i checked mine. I've thought for a while my engine seems just slightly rough but not down on fuel ecomomy or noticeable power loss. I have had what sounds like one of those old policeman's whistles going on under load but only barely noticeable. Anyway, lo and behold- the front lower stud is missing. No sooty deposits around the manifold but then its a bit dirty anyway, nothing extra though. Running fine for now, so one for the to do list.
Still..... ARSE!!