I have an ls/vtec in my 2000 civic si. AEM cold air, dc header, skunk2 itk manifld, aem fuel pressure regulator. I have new spark plugs, cap & rotor, & engine wire harness, w/ stock si ecu. My CEL is on w/ knock sensor circuit malfunction & catalisist below threshold codes. The vtec will engage with the CEL on everyone tells me this is impossible... Is it? If so why does my vtec engage?