Those "shorty" headers have been found to do very little in any gains. Be prepared for a very loud exhaust if you are running with very little back pressure / muffler in the rest of the exhaust. Why are/do you want to pull the CAT?
The companies that do make an off road pipe usually expect a full length header. Pulling the CAT alone will not make nearly as much performance as pairing the off road pipe with a good header
2001 ZX3 2.0L Zetec-
Hatch Nation #42
Going through Rebuild See "The TICK Build Thread" for details (http://www.focusfanatics.com/forum/showthread.php?t=289168&referrerid=62897)