Let me clarify my experience a little bit here. I was not getting a CEL when the car has an anomalous shudder at cruise, 80 MPH 3300 RPM. I have been calling this a misfire. This may not be correct but to the best of my knowledge i think thats whats happening. It usually happens after I let up off the throttle a little. I never get a CEL when this happens. On one occasion I had my data logger on and could not find anything on there, no spark retard or exessively high knock voltage.