sound in rear end

[CrimsonRacing]

Michael,
I also have another question to pose to you.

I am making the change to underdrive pulleys and have gotten quite a variation of replies.

Should I use a regular overdrive pulley on my alternator to sustain hig voltage or will a underdrive pulley on there as well will give me the charging I require.I have working a/c and a stereo but not one of those booming things.Also.......approximately what kind of hp increase would you feel I will get with the ud pulleys?

And.............which brand of UD pulleys would you reccommend.

thanks,
Crimson