There has been a lot of buzz lately about TJ owners wanting to use a K&N air filter. K&N does make a filter made to fit in the TJ's stock filter box, however to get a better gain in performance, you can follow one of the following links to learn how to use an open coffee-can-style filter. The mod. takes about ten minutes and any idiot with a screw driver can do it. Filters are available here.
Editor's Notes: This may not be street-legal in your state and may also void your manufacturer's warranty. Check first. Also, K&N is a registered trademark of K&N Engineering, Inc..