odd idle problem
 

well, what happens is the car will run fine, idles around 900 right now, but occasionally, for about 5 minutes it will want to idle at 100-200.. it will be very choppy and die sometimes, but after about 5 minutes it will be back to normal. any ideas on my problem? im thinking theres a solinoid that is opening a vacume line that is leaking, but then again i can disconnect my brake booster line and it will hardly drop the rpms and thats a pretty hefty vacume line. any suggestions will be thanked!

what i have tried-
cleaned up the carb
got new plugs
got new filter
checked for sparks
checked for loose cables to the coils
checked the dizzy

its a 1980,12a, racing beat exhaust

doesn't that drive you nuts,,i did the same,,,it turns out
to be a vacume failure,in my case,,the shutter'coasting'
valve.even,,today i was under the car and noticed a
gash in a hose,,i'll fix that tomorro,, but with all those
hoses,and the hi heat of the rotory,,hoses go all the time

allright, I guess i'll just be buying a couple feet of vacume hose then, thanks!