Question for the board

[Silverbird2002]

I have a 02 firebird, Lately everytime I go to start it up my car runs rough. Only when it is first started and when it is ideling though doesnt do it all the time and if you give it a little bit of gas it will go away. Also there is a hum and or a whinening sound comming from the rear of the car I noticed it the other day when I was driving it seems to only happn at speeds of 50 to 55 and then seems to go away. I told my friend that I work with about it and he said it may be a bad wheel barring. Also I have one last thing. I noticed when I start the car that there is like a ratteling sound comming from somewhere....it sounds almost like a heat shield or something but I checked the heat sheilds out and they all seem to be ok....could it be spark knock???? If so should I chang my wires? I have new plugs already so I dont think they can be that. Anyone have any clues as to what some or all of these troubles could be caused by?

Thanks again all

[Fbody3400]

Could be a bad cat. Also, i've seen new wires go within days, so dont factor that out.

[Silverbird2002]

yea that's what I was thinking aslo.....thanks Fbody. I'll check that out and hopfuly that will be what it is. thanks again