So on my 03 f4i completely factory, i had a -1tooth front sprocket on, and now it like whines and more so at high rpms. could it be that they tightened down the sprocket to much?

 

I wouldn't think that they tightened it down too much. I know the stock ones are on there REALLY tight. Check your chain for the proper amount of slack. I do not know if a loose chain would make that noise, but it is something to check.