got vibrations!!!!

[robertsafc]

Hi, got 320d automatic touring, not had it long and i love it.
I have just finished fitting sat nav/tv rear screens and dvd player, i love the car !!!!But!!! i keep getting vibrations when i am just feathering the throttle once i have achieved my speed and if i acelerate softly the vibrations are horrible, but if i am to floor it there is nothing????? it seems as if something is out of ballance like propshaft, gearbox, diff??? hope someone out there can shed some light as i dont want to get rid of it. thanks
rob