Over 4000 RPM Vibration (Driveshaft?)

I have a vibration over 4000 RPM. I made a search, and I don't think its about my FLywheel or ATI Damper, because I had this vibration before I got my new 383cid and Viper Spec T56 trans.

Whats the problem? Could be the driveshaft? I have stock balanced driveshaft btw.

I have the same thing on my 3rd gen (which has the 1LE aluminum driveshaft). Never had mine balanced or taken out. 3rd gear (A4) is pretty noisy once I get up there in the revs.

Today I tried to get it balanced, but they couldn't do that. I mean it didn't worked.
I have the sound like a massage seat. The sound starts around 90 mph at 4th or 5th gear.