Rear end problem help

Alright guys well reporting back on the situation. So after talking with this guy about it that i got it from online he insisted on putting some miles on it and working it in . Well i did and yes the clunking did go away but the howling at 40-30 is still there. well i waiting to call him since we had thanksgiving and everything. So i called him today and he asked me if i had green bearings and i told him no i dont. Well he insisted that he would send me a free pair of MO green bearings i guess. So i then asked him that okay so if that doesnt work then whats the plan?(this is the kicker) So he said well then i would just have you send the unit back and issue a refund cause i dont know what else could be wrong with it....I said theyre is no way we can open it up see if something is off or something? He then replied to me saying something about he didnt build the unit he just sells them....So now im not really to thrilled about this and now debating about just pulling it and sending it back and going with dr diff or a reputable buider because im tired of the sound of a jet plane landing in the rear. Could green bearings really make a difference? My bearings are brand new stock tapered greased and all good?this has been a headache. Let me know what u guys think?