Hi new guy I put K&N replacement filters on my 04 n/a and noticed nothing other than a 70 dollar charge on my VISA. They dont do much but if you want to keep the stock air box then it would be a tad bit better than stock. (do a search about grill mod, a mod that chops a bit out of the stock grill for better stock air intake. I put a magnaflow 14861 dual tip muffler. I got a TVT cai but alot of folks like needswings alot...just cost a bit more. Sprint booster is a good topic to search...it has pros and cons.

Id love to help more but the wife and kid are hounding me to go shop or something...God help a guy that stands in the way of THAT
PM me if I can help you further. Search the forum too, theres tons of info.

Good luck

Curtis