well six have you looked closely at the dist? I don't think the 87 had the dist you describe.. All I have seen had an adjustable dist..
First thing I'd advise would be to take the hose loos from the vac adcvance and put it in your mouth and suck on it.. to see if the vac advance is working or has a hole in it..
If it is working then run the jeep with one cylinder at a time off the plug to see if you have a dead or partialy dead cylinder..
Also you could have a partially stopped up muffler or cat.. But from the missing at idle I'd suspect a bad cylinder.. could be either the plug. wire or even a burnt valve.
Big JIm <img src="/forums/images/graemlins/pfft.gif" alt="" />