Rough idle when warm

I've replaced almost everything that I thought would fix this. Spark plugs, wires, cap, rotor, motor mounts. I've done a lot. I've even took it to a shop and they were confused as well. I'm thinking that's just the way this car is going to be, but any advice to possible fix the issue would be great. When I say rough idle, I mean the car shakes a lot in drive when stopped and idles lower then when in neutral and park. In park and neutral the car is much better but noticeable. Is this only for carb engines? I have the fuel injected model