Hello. I have a 2002 Xterra with a 3.3. It started running rough and I thought I had just got some bad gas. Turns out that is not the problem. I purchased a OBD scanner and got the codes off and they are P0300 and P0327. I have replaced the knock sensor, plugs, wires, rotor button, and distributor cap. Still no luck. Now sometimes it will run and do ok but 95% of the time it is missing. What am I doing wrong?