engine noise only when in FM mode

hey, thanks for reading, i just bought a pioneer gead unit, avh-p6500dvd, and the installation went fine but now when i am listening to the radio, TUNER mode), i can hear my engine whining up and down as the car accelerates. I have an xbox hooked up as my AUX VIDEO input, and when i am in AV INPUT mode i get NO noise. Also when i am watching a dvd from the built in dvd player function, i also get NO noise, its only when i am in tuner mode that i can hear the whining. Also, my FM reception is very bad, the stock Nissan radio had good reception and i figured the new unit would have even better reception. Any ideas or input will be greatly appreciated. Ill recheck my connections later tonight, maybe its just a loose antenna cable...thanks

ps: the car is an 02 nissan altima

thanks forbidden, ill check that 2nite when i open the dash back up and ill make sure it sits away from the headunit power cable which is really the only power line  i have runnning through that area. everything else is the audio/video coming from the xbox and the video rca going out to the rear lcd's. ill prolly just take it all out and test then.

DYohn, maybe i didnt notice it when i installed but i didnt see any ground cable to the antenna. i only saw two ground labled on the headunit. One said GROUND and i could tell that was the GND for the entire headunit. the other one said AMPLIFIER SHIELD GROUND ,and that was labeled on the wire harness that i bought from crutchfiel, i didnt know where this one went so i just covered it with electrical tape. The antenna was only one back cable which plugged into a converter that was provided by pionner and then that plugged into the hideaway unit.

thanks

looks like i fixed the problem.

i followed your advice forbiden and i repositioned the hieaway unit and separted its cables from the antenna cable, now everything works fine with no noise. Thanks for your input everyone, i can now enjoy my new HU.

rgds