I would agree, it sounds like a bad knock sensor or the computer is having heart burn. If the computer can't retard timing enough to stop knock, it is usually a bad sensor, but it could be some really bad gas
(in the fuel tank). If it is misfiring, the idiot light and message should come on, and then it could be a bad intake valve on cylinder one.
Good part of that is new cylinder heads are hardened to prevent any further problems, new procedure with a new tool, cuts the repair time in half.