Truck hates idling???

[mprobst]

I changed my glowplugs, and 2 weeks later had p0603, P1316, P1247 and P1272 codes. thought I had a bad harness under valve cover, took it all apart, put it on meter and showed OK, so put the spacer in the connection to keep it tight, cleared codes and it ran well on test drive, except one miss and threw 1277 code. drove a few more miles, and no issues. cleared code and ran 2 buzz tests at home, and could not repeat code. This morning on the way to work, stuck in lots of traffic, and crept along at idle speeds for close to 20 minutes, towards end of that time, truck started missing and service engine light came on. I was able to run about 3/4 mile at 50 mph, and ran pretty rough until I pushed it a little to get up to that speed before hitting traffic again. the fast run cleared the code, and truck ran fine at idle again during next short section of slow traffic. This made me realize that the first time I had the issues, I had received a call on my cell phone, and sat in the parking lot talking for about 5 minutes with truck idling, went inside for 10 or 15 minutes, and came out and started truck, and service engine light and truck started missing leaving the parking lot. Is this a symptom of a bad IDM or PCS, etc, bad fuel? or do I have something fouling my injectors if I sit at idle for a while. anything I can do to avoid this besides not idling? when I come down from the ski hill most weekends, it is coasting with truck in 2nd to keep it slow for about the first 15 miles, I am guessing this is going to happen there next, and I wont really be able to get on it to clean it up.