Hello

Got to wonder about the motor mounts on this one. The reason is it only does it in drive. When in reverse the engine is torqued over to the other way which would lift the motor off the bad mount. Right side mount is most likely settled and giving you the feeling it is idling rough or missing. When engine speed is increased the harmonics go away which is why you don't feel it anymore. If you have a floor jack put a block of wood on it and jack the engine up just a little bit and see if the vibration/miss goes away. WARNING! Do not jack the engine up to far or the fan can and will hit the shroud. Check that the fan is clear before starting the engine. Also use a big enough block of wood to distribute the weight of the motor without cracking the oil pan. I know it sounds crazy but it could be. I've fixed many rough/missing at idle complaints with nothing more then mounts.

Outside of that it could be a lot of things which can only really be checked out with the proper equipment like scopes and scanners and such. Good luck!

fasthair