Vibration on Acceleration - not typical

[The Walrus]

Funny thing in my 91' NX2000. It vibrates on hard acceleration - no matter
the speed really, at WOT the car vibrates, or shimmies is maybe the more
appropriate term - it's most noticeable when you're holding the steering
wheel, and less apparent when you're not.

The motor mounts are all in good condition, and it's not present at WOT when
at a stand still, only when accelerating, in fact, it does it when
accelerating even at a relatively normal level - but not as bad - when you
reach your cruising speed, or any constant speed, it mostly goes away.

I COULD blame the cruising vibration on the harshness of the suspension -
I'm used to a 93 1.6 sentra - which is squishy. My Mechanic suggested the
axles - said that's where to start, but it "could be anything". one ofthe
axles I replaced from napa due to a busted CV joint (passenger side) -
perhaps I need a new drivers side one too? or could it be the tires are out
of round or maybe... is the car just supposed to be like that? it's fairly
pronounced - yes I checked the faq, SE-R.net, and the forums.

I guess what confuses me is the fact that it's so pronounced at
acceleration, and not when reving standstill or so much when just cruising,
or even maintaining a constant speed at high RPMs!

let me know what you think - publicly or privately.