Well just a update, went down to the machine shop to drop off my genuine stem seals and for some reason all my exhaust valves have a slight bend in them which they found when spinning them up to recut them so they are only cleaning on one side. Very strange, but I have a feeling this may have been the slight "popping" sound on idle which it had intermittently. But as for make of valve I think ill go for MAHLE valves as they are a good german engineering company.