Here's a short video of my Duratec ST24 with the following mods: custom K&N pod style air filter (similar to 57i kit) with CAI, optimised TB and the rear LHS muffler removed.
The car is in second gear (MTX) and is accelerating up a very steep hill. All the windows are up. At normal cruising speeds the cabin noise is no louder than a standard ST24 (I like it that way for long trips).
See the link in my signature for more details of the mods.