After my 91 Escort GT has been up to temp for awhile and the outside temp is above 80 degrees my ignition starts to miss. It is ONLY UNDER 2K RPM and when there is a load on it like the A/C it does it more. Once it starts happening it will keep getting worse until it will miss at idle every few seconds and I have to slip the clutch to make it stay above 2K to get it moving. If I turn it off for a few minutes then restart it, it will be fine for the about the next 15 min. I had an MSD box on it which I took off, didn't help, gapped the plugs smaller since I opened them for the MSD, didn't help. The plugs only had about 1K miles on them when this started to happen. I checked for breaks in plug wires, made sure they aren't jumping each other, and checked the resistance of all the wires which were all high but within a reasonable amount of each other. Cap and rotor are new and looked ok. I think I have a bad spark plug or crappy wires. Could this be a bad TPS? Whatever it is it has to do with the outside temp being hot. Any Ideas?