Can i ask why you arent running the F series plugs? The C series are for offroad engines and from memory are slightly longer in the body. I mistakenly ran c series plugs one before and had the same problem as you. I even changed plugs and restarted the engine got out of pit lane into turn 2 and it stopped. When i realised what plugs i had, i changed them back to F and problem solved. Hope this helps