[Phast SVX]

So....here is where it starts. The extension fit in after my mechanic had to have it modified to bolt in,it appears it was inadvertantly unfinished, but i now have reason to believe it may be too long as well. When you rev the car in neutral, no vibration occurs at all. But when you start to accelrate, there is a tapping sound that occurs intermittantly and seems to be at your feet, so obivously its the driveshaft tapping on the floor of the car, depending on how much throttle you give it. the driveshaft is properly installed, as we did it 2 times to make sure.
my scenerio to help explain:
:while cruising at speed:
It does not occur while cruising at speed off the throttle in gear(which means the driveshaft is spinning with the speed of the car and no vibration or tapping is occuring), and with low throttle it does not occur at all in higher gears. With alittle more throttle, say driving 30 in third gear, it will begin to rather intermittantly make a tapping sound, which with more throttle speeds up into a thump. My thinking is, the driveshaft is to long, so that when the drivetrain tourqes on the knuckes, the shaft is bowing and cuasing the tap/ thump on the floor. I know its not the clutch(new ACT 2600 kit) its deinftly a driveshaft issue IMO, and the trans, along with every other aspect is beutifull.
hopefully someone can help me out with my diag,
phil