thanks all for so many possible scenarios
i just soundproofed the interior of car floor and doors and the trunk
and ...
i took slowly one by one in consideration the suggestions u guys made, and i hit the wall .. i need to suspend it to actually see if anything is wrong since on the stock stand, i can not do a diagnostic... i'll have to visit the mechanic's crane
.
(the cv joints seem fine.. they wont say peep at moving full turned left and right; under the seat is nothing; i stripped the car to metal, and put silicone gaskets on every screw underneath (heat shield , exhaust, and some other etc.))
Edit: what is the rear parcel shelf? on the back there is only the gas tank and the cat-back ... the tank is bolted in to the structure.. and the exhaust pipe hangs there freely:)