I have a 2003 that is throwing P0307 cold only when under load. If I clear the codes, and restart engine, it only comes back after I am in drive and start driving for a few blocks. If I claret our, it doesn't come on while idling, only after I start giving it gas again. I have swapped the coil with another cylinder and changed the spark plug to a new one. There is no oil around plug, in the intake, and the old plug was not particularly fouled. Any suggestion on what could be causing it to only accuse once I start driving and not while idling in place? Thank you.