88 2.9 strange problem?

I have a 1988 2.9, 5 speed, 158K great shape and well maintaned. This problem started about 6 months ago. It happens mostly at interstate speeds. I can be running along and it will start to run rough and chuff out black smoke. If I pull over, switch it off and wait 3 or 4 mins. Recrank it will run fine. Here is the kicker. It may not do it again for a month or two?
Since this started I have replaced the FPR,ECT,Temp sending unit,checked fuel pumps and pressure, replaced the fuel filter, anyone got any Idea?

Had the same problem on my 87 ranger 2.9 . Replace TFI module ( ignition module ) and stator on distributor. Unfortunatly this repair takes months to confirm if it's fixed since it is so intermittent. But chances are, that's the cure.

I'll give that a Shot. Thanks