I've been having that problem with my cylinder 4. In addition, I have been burning a lot of oil just at startup and when the engine is being driven by the car with the throttle closed.
I have had a lot of buildup on the spark plug, and had a compression and cylinder leakage test done today. I only have 85 PSI of compression on 4, and the leakage is 100% through the exhaust.
I just joined NASIOC today, and am not permitted to start a thread asking for information about getting changing or rebuilding the head, this is the closest thread I've found so far.