1.6 auto ford fusion bad vibrations

Hi

i've trawled this site and some others and can't seem to get much info. hoping someone can offer some advice. I've also posted this message on the ford fusion forum; hope the repeat post isn't bad etiquette.

i have a 2004 ford fusion 1.6 automatic - only had it a month or so. Around town it's fine but when driving at speed, at about 50mph and above, i get a lot of vibration coming through. However, the steering wheel does not shake, just what appears to be vibration and shake from maybe the bulkhead and by the gear lever - it's roughness as much as it is vibration, i guess. it doesn't happen when the engine's revved in neutral. i've checked and had all tyres/wheels balanced, checked bushes, exhaust rubbers and the exhaust shield. everything seems okay - i reckon it could be an engine or some other mounting problem, perhaps even a dodgy fitted or leaking manifold but again, everything's fine when revved in neutral. Any advice greatly appreciated as at at present, travelling on motorway at above 50mph is a nightmare! thanks and best wishes. mojo