I recently installed a cd changer in mercedes benz S430 yr 2000 in the trunk. t?

the FM modulator was placed under the rug besides the inner console behind the gas pedal.Recently when im driving the radio stations reception are not clear and sometimes there is no reception completely. i drove to person who installed the cd changer to me and he says that nothing can be done, is that true. i do not know anything about installation. Initially at times i could hear the sound of the car when accelerating.What might be the problem?any people out there who have knowledge installing cd changers? helppppppp!