[JL8Jeff]

Does it sound like it's coming from the engine compartment or possibly under the car like an exhaust leak? Check around the catalytic converter on the passenger side, it might be leaking where the y-pipe goes into the cat. Also check the AIR connection to the header to see if a bolt or nut loosened up. Also check the header where the AIR fitting and EGR fitting is welded to see if the welds might be leaking. It also might be worth doing the oil change to see if it goes away. The rear passenger side spark plug and wire are a PITA to get to. I think I ended up removing the AIR fittings and pulling a coil or 2 to be able to reach back to the last plug/wire.