engine or transmision

I have a check engine light on which was decoded saying it was the EGR which i replaced a few years back. my problem is that when i get up to go between 52 and 78 mph it starts to act like I get a massive miss in the engine, but quits if I gas it. I have been working on cars for years, but this is a new one. Would the EGR valve make it cut out at certain rpm or would it miss all the time? It did not do this before I replaced It last time. As bad as it shakes when it does, could there be something going on with the transmission? It seems to be shifting normally, but with that kind of vibration I would have to drop more than one cylinder.