If you're hearing the knocking, it is unlikely that the knock sensor is faulty. The knock sensor is designed to do exactly that - detect knock, feed that back to the
ECU, which will then retard the timing of the spark event.
Knocking can be caused by poor fuel (not in your case, using 98), carbon build up on the top of the pistons (use a bore scope down the spark plug hole), or a lean fuel mixture. Causes of lean fuel trims are vacuum leaks, reduced fuel delivery / fuel pressure (eg. weak fuel pump, restriction in fuel lines, dirty fuel filter) or clogged injectors. I don't think you car has a
MAF sensor, but a dirt
MAF sensor can also lead to a lean fuel mixture.