Hyundai Repair: 01 Elantra Rough Idle, intake manifold gasket, vacuum leaks

Question
No MIL or pending codes, new plugs, wires, injectors, coil packs.
At idle, there is a noticeable vibration that I can't seem to resolve.  Can't detect any vacuum leaks.  Runs fine on the road, but the vibration is not right, feels like a miss, but not.  RPM doesn't fluctuate, stays around 700 on the tach.  Any suggestions?

Answer
If the vibration is the same frequency as a misfire and occurs only at idle, check for a leaking intake manifold gasket.

If the vibration is a higher frequency than a misfire, you may have an issue with a motor mount transmitting too much normal engine vibration to the body.