I just purchased an 04 GXP on Saturday. I almost immediately starting looking for performance mods and found this forum. I love the look of the car and the way it drives, but I do want to add some HP and Torque. This site has a lot of good information on it and I look forward to hearing what everyone has to share about their cars. From what I've read so far, it looks like adding the K&N filter is about all that is out there so far. Does it make that much of a difference?