Ah I was right then! 1. The sensor is under the inlet manifold. If your facing the engine bay, then its on the left of the inlet just underneath it. 2. The wire might have been cut or damaged. It's only a single wire so can easily break, had the same problem in the past. 3. As long as you get it sorted you'll be fine. I think the ECU will go on Safe mode if it doesn't get a knock reading. The car will usually go shit slow too, well our old GT did. It didn't even boost proprly, but once the knock sensor back on it was flying again. Hope that helps.