Knock Sensor Code
 

I recently replaced both of my oxygen sensors and the car has been running much better, and my fuel mileage has also improved. The problem is that the ECU is throwing a 28, refering to one of the knock sensors. The check engine light comes on randomly and may only stay on for a few seconds. The car drives and runs great as far as I can tell. Should I go ahead and get the new knock sensors? I know to replace them in pairs, and that they should run about $30. What are symptoms of a bad knock sensor?

i am not sure on the details but i woulld assume that the car would advance more timing with a bad knock sensor unless the ecu can see that its faulty in which case it puts its self in 'limp' mode where its super conservative with timing.