Someone on a jeep forum (you guys have been more help) said "it has to be a bad head gasket".
I've replaced a few head gaskets and this one has no symptoms. Pressure test is good, nothing in the oil, nothing out of ordinary coming out of the exhaust. Not gassing out of the radiator and not leaking a drop anywhere, nor is the coolant level changing. Also seems to be running great and each exhaust port is within 10 degree of one another.
It's not an uncommon problem on the 4.7 v8s. Like I said my parents was doing exactly what you described for a couple of years before it finally got worse. The mechanic I mentioned earlier has spent his life working on Jeeps and has owned a couple of 4.7 v8 WJ's. If it's a cracked head gasket, depending on the severity of the crack I could see it exhibiting exactly what you're describing.
