Got my velocity stack yesterday and took apart the air box and installed it in less than 10 minutes...longest part of it all was allowing the instant gasket to set overnight. Installed this morning and after realized that it does add a slightly louder tone to the exhaust. It's most noticeable when at cruising speed and gas is applied suddenly. Also, it seems like the engine sound is a little louder as well. Upon accelerating it doesn't seem to make much of a difference other than it feels like the car has slightly more power throughout the entire band, but then again that may be more of a pseudo effect. I will have to report again once I go on a long distance drive on the highway. So far so good though and I'm glad my '03 is now up to date kind of lol.
So far I have K&N drop in filter, Skunk2 plenum spacer, and velocity stack. Have to wait to get some HFC's and possibly Nismo S-tune Muffler and then it may be time for Osiris UpREV as I do feel my car may be in need of an air/fuel ratio adjustment.