Thanks for reply. I had a shop look at this and their diagnosis was a bent drive shaft w/recommendation to replace ds with a new one at a cost over $1000!! I don't agree w/their diagnosis - - especially since they never even mentioned the other lower cost solution (having drive shaft straightened and rebalanced by a ds shop).
I just had new tires put on car - balanced and realigned - so I don't think it's related to wheels. I get vibration under normal acceleration & cruising - and it doesn't change or dissapear when I shift trans into neutral and let car roll @ 35 - 40 mph - or doesn't change if I downshift. At higher highway speeds (60 - 75mph) the vibration is not noticeable.
I figure only way to find out is to drop the shaft and have a look.
I wasn't aware that E320 coupe had two flex disks. Are they both identical ? (I'm working up a parts needed list)