I know this post that I have found is a year old but it is the exact same problem I am having.
At first my car wouldnt start at all the spark was very weak yellow apark at the plugs.
Changed the plugs cap and rotor car started but runs rough at idle through mid range.
Am planning on changing the wires but have a question about the spark plugs.
What brand is the correct OEM replacements? Whats the correct resistance? whats the correct gap? and what Part # are they?

All the info I have found suggests a platinum plug but I know they didnt have platinum in 87.
Also my ICM has a silver metal cover over the area where the heat paste should be can this be removed to replace the paste or should I not mess with it. dont wanna buy a new ICM there a bit spendy.