hi, ever since i replaced my alternator with a highout put one with a overdrive pully it has been making this weird noise at idle and when i reverse. now me and my freind both took turns looking under the hood to see what the noise was coming from and we both came tothe concuslion to replace the idler pully and the tensior. now when we went to go buy the parts the place where we brought it said it could be the srepretine(sp) belt and since it was over a year old and only 25 bucks we said why not. now when we put it back on it lasted like a week before the noise came back. is it possable that the pully is putting to much stress on the tensioners. and also when we where done we did have a bolt left over would that be making the noise.

I find it normal to have parts left over after a repair....
That "overdrive" pulley. Should I assume it's aligned correctly? Correct groves on it? Hopefully there's some play left for the tensioner.

It likely was not the belt in the first place. It most likely is the tensioner. Now that you have a new belt, all the better.

From a practical, common sense view, having left over parts from completing a repair is not a good sign. Its placement in the first place must of had purpose or it would not be there to start with.