After my previous post, where Bushnut helped me figure out what was causing my misfire was just a thick layer of oxide on my distributor cap, I'm now dealing with p0505. I haven't had the car run without a misfire since rebuilding the top end, I attributed the idle issue to the misfire, because it was so pronounced. I've spent the rest of the day driving without incident, but racking my brain over the p0505. I haven't seen much on xterras in particular, but for for other nissans, when the IACV fails, its from coolant shorting out the motor, which then shorts the ECM. hoping I caught this in time, and maybe I can save someone else a few hundred bucks.