The valve clearance was done recently and rechecked yesterday, no problem there.It proves Miglia's point...they do like new plugs !...did you gap them all ? have you checked the valve clearances ?
New condensor fitted ?
Wondering if its the grade of plug with it being colder air than 'normal'....
On Std 998 we use NGK BP5ES, not sure what plugs you run ?
The plugs have the correct gap. I am using bp6es at the moment but I have just bought bp5es and will try them later today.
Thanks