Audio Systems: engine noise, resistor type, saturn sl1

Question
I recently hooked up Sirius radio in my 99 saturn sl1.  I never heard road noise but now I do.  I disconnected the sirius all together and can still hear it on any talk radio but it is not to bad when muisic but i think that is becauuse the music drowns it out.  I have tried to run new power from the battery to the radio and  a new ground from the radio to the point that the battery attaches to the inside fender wall I have had the sirius hooked up to the factory radio supply and the the new power I ran from the battery and still nothing.  Any suggestions?  I have heard that maybe I need a filter on hte alternator.  If so what type and where do I get it and approx cost if possible.  If not what is next?

Answer
you weren't very clear on what type noise it is. whining, rushing, a squeal that changes with engine speed etc. with info given, i would first try resistor type spark wires and plugs. if it's a loud squeal, there is a major possibility that the only way to reduce it is with a new alternator. does it do it with the engine off?