Removing either of the two pre-cats would trigger the check engine light. Most people just leave them alone. Check to see if your main cat has an O2 sensor on it (I've heard some WJ main cats have them and others don't). If it doesn't then you can cut that out, if it does then go for a Magnaflow hi-flow cat. Just my 2 cents!
2004 WJ Overland 4.7 HO Graphite
~110k miles / Powerstick Muffler / Superchips Programmer / Bilsteins 4600 HD / Addco Rear Sway Bar
2004 WJ Overland 4.7 HO Inferno Red
~93k miles / Flowmaster 10 series / exhaust cutout / K&N FIPK Intake / Jet Performance chip stage 1 / Superchips Programmer / JL sub and Alpine amp / RIP 1/17/12
1998 ZJ Limited 5.9 Deep Slate
~101k miles / Doug Thorley headers / 1.7 Harland roller rockers / Magnaflow hi-flow cat / no muffler / K&N intake / Bilsteins / 242 / SOLD!
2010 WK Laredo X-package with Hemi (parent's Jeep)
Youtube Channel (4wheeler14)
WJ Build (aka Maintenance) Thread