I havent done a timing belt before, nor have I had much experience with it, but I'm a 1st year mechanics apprentice. I was talking to one of the mechanics at work, and he was saying that all timing belts make a noise, before they are automaticly tensioned, which makes them too tight. You cant adjust it without taking the whole belt off, and it goes away after a while. Most timing belts are the same, so you'll get it no matter what you do. Just live with it, make your exhaust louder (like mine, i cant hear the engine ), or turn up the stereo!
Btw, a tight timing belt doesnt not affect power what-so-ever