Maybe you guys have thought of this before but I'll just put it out there in case you haven't. I picked up an infrared temperature thermometer/detector from Radio Shack a while back. You can get them just about anywhere but the Radio Shack unit is small enough to fit in your pocket, about 3" by 1". Whatever the case, I've been using it on all sorts of stuff. Test tires on your trailer or truck to make sure they're properly inflated. Check engine or radiator temperatures for diagnostics..etc. However the BEST use for it so far is for determining which plug is misfiring on my XLT. With three cylinders you would have to remove as many as three plug wires to decide which plug is not firing, and even then sometimes its a little difficult to see which one is not working, or if its two of them! All ya have to do is point the sensor at the exhaust manifold right where they bolt on to the block and instantly see which one isn't working. It will be REAL obvious. The fouled plug yesterday was running about 109 degrees and the other two were running about 250-290 degrees F. I would imagine the 100 deg was due to the heat transfer from the running cylinder, or possibly an occasional missfire when it cleared up for a second. I'll be bringing mine on the trails this winter...it isn't as good as an EGT but at least it will get you in the ballpark when it comes to troubleshooting.