I agree with Doctor about checking your shims. If you are running 30% you need at least 1.0mm for shims. You sound as if your timing is way too advanced. Try a cooler plug. OS motors try the R5 or A5. (cold plugs) or no. 7 for turbo applications. They have thicker elements in the plug for high RPS and high nitro. Shimming it out and a colder plug will give you better performance and longer plug life.