strange wobble...again...rear this time

[gitchies]

So, last week i had this strange wobble...got it checked out..turns out, i had a warped rotor...so this past weekend, new pads and rotors....
now, i still have this slight wobble coming from the rear passenger side..i think. i just know its the rear.
had my suspension checked out about a month ago, did an alignment about 3 weeks ago...everything was fine according to my mechanic....
so now i still have this slight wobble going above 80km/h....sometimes it disappears for a few seconds...then comes back...
my suspect is, some sort of bushing? or could it be a bad tire?
any thoughts? this thing is driving me nuts....argh...
2002 4.4, 61,000 miles....