Hydroboost all the way for me. Holds 15 to 18lbs of boost. No Problem. I went with the expensive kit, but you don't need all the bells and whistles. A base kit or refit from a Astro have yielded great results. There is nothing wrong with Vacuum either except the Hydroboost will hold more boost. The Powermaster worked great in my books too, I just couldn't trust it's reliability after it just about got me killed.