Why are you using 93 octane? Have a tune or some other reason? Unless you have modified your car with a tune going with a higher grade fuel us just wasting money.
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)