I just picked up a 01 Suburban with 117k miles on it. The past owner said to run 93. Pretty sure this engine doesn't require higher octane. The ses light came on after I filled up with 87. Bank 2 knock sensor low input. I have read that these engines are prone to buildup. Will seafoam on a low tank do the trick in knocking the carbon out? Or do I have to pull the intake and replace the sensor?