If you have a lot of engine mods (supercharger, turbo, etc.), you need extra fuel. More than the stock pump can flow. All high output fuel pumps are loud. I had a Walbro 255 in my old turbo Maxima and it was loud, but during normal use not that noticable. Let's face it, most cars running these pumps are already loud. I know that I barely ever heard mine during driving, but I had no cats or resonators in my exhaust either. The Walbro was probably a little quieter than the Vortech T-Rex aux. fuel pump that I tried out as well.