prob engine mount but with out hearing it, it could be a few things! like cv's.have a look at the mounts and see if the rubber looks ok,try and see if you can get some one to rev it,it may not move to the same point as loaded but you might hear it from the engine bay.see if you can physiclly move the engine about or put a jack under the gearbox and slowly push the motor and box up see how far the mounts move! and put the jack on a strong part of the box.or if the gearbox is close to needing an oil change drop the oil out and look for metal.
mick