need advise: driveshaft problems i think

[project 67 sub]

ok so i took my driveshaft down to a driveline shop yesterday(the 16th) that builds custom & high performance driveshafts(they have been their a while and heard they do good work). took it down because mine had a wobble while driving. well after i got it back he said that every thing is good to go now but it was pretty bad before he started(he had to fix the splined nub on the end cuz it wasnt welded on strait), drove it for a while like that but not on the freeway. it now has a new carrier bearing and fairly new u-joints still. but here is my question and problem: when i drive it on the freeway it feels like it is vibrating pretty bad and i dont know why because i just had it fixed, is their anything else that i can check that can cause this?
any help at all would be very much appreciated