Try rotating the drive shaft 180 degrees? I had a similar vibration once and this did the trick for me.

What is the angle between front yoke & driveshaft?
Without cutting the floor to raise the tailshaft, I've seen too much angle.

Ok just dropped her off at the dyno shop to get a CV joint put in...hope this works...will let you guys know when i get her back...wonder how much HP loss moving from aluminum to steel shaft...:rolleyes: