Just lately I've had issues with the knock sensor code popping up and a light engine ping at hard throttle. This is a rebuilt motor with maybe 30,0000 miles on it and so far has run like a champ. Today I changed the fuel filter with a MANN filter and added some Seafoam to a full tank of super unleaded. I also used the seafoam you spray through the intake to clean out deposits in the intake and other places, but this seemed pointless as all this was cleaned during engine rebuild. The fuel pressure regulator is new, but I do get the faintest smell of gas from the vacuum hose when I pop it off. The car just passed emissions before the problem started and not sure if this matters but the NOx was 1517 ppm which is just below the 1522 ppm necessary to pass. the hydrocarbons where 78ppm, way under the 216ppm. I'm not sure if any of this info is relevant but you never know, well I don't anyway. Thanks in advance for any input!