Intermittent Bad shaking at idle?

[84convertablegt]

My 3.0 has 235000 miles on it now. Still runs great for the most part. I have one nagging problem that I've tried everything and thrown money at to fix. Sometimes at idle, like when stopping at a light, the truck will start to run rough. It doesnt sputter or anything, its like the motor just starts to shake badly. If you give it gas, it will smooth right out. This is only sometimes, I cant seem to figure out what gets it to do it, except that I usually notice it after a WOT blast on the highway and then come to a stop, it will be doing it.

I have replaced the balancer, the plugs, wires, coil, fuel filter, synchonizer, EGR sensor, etc. I've cleaned the MAF. There are no codes present at all.

I was thinking maybe a motor mount, but its so intermittent that I can't tell. Then I though maybe EGR related, but there is no code so could it be EGR?

I've checked all vacuum lines. I am really at a loss here. Im almost ready to take it to FORD. Any educated ideas?