connects to the pin on the cam. Its has teeth on it and if the CAS is not aligned right (heads not machined correctly) the teeth can wear making your timing jump all over the place. Have you checked the timing? Is it always the same? When this happened to mine the timing would be at a different value every time I checked. Sometimes it would be at 15 sometimes at 18 and one time it got to about 10. New CAS solved the issue.