Okay well now that I've played with the timing a bit it's apparent that the Eagle isn't liking the diet of 86 and both sea level and high altitude (above 3000 feet) driving. You can tune for above or below and 90% of the time it will be behaved but the variance in air density means somewhere along the line you're gonna get some wicked knock.
This is fixed starting in 1984 with a redesigned (okay, internally it's the same microcontroller) computer that includes a knock sensor, but I'm an 82, so no knock sensor. Of course, there's a fix for that.
They don't normally come up for sale often but it's great for adding a knock sensor to a non-equipped engine and it supports almost every ignition type. Popular Science positively reviewed it in 1984 and yesterday found one for the equivalent of "half price" in 80's dollars...but it's going to a PO box int he states so it's unlikely I'll be able to install it for a while.