Re: 03 WJ 4.7 with 192,000 miles - replace catalytic converters?
For best performance I would replace the y pipe with cats, and put in new o2 sensors to play it safe, the OE denso sensors are fairly inexpensive on rock auto. You can also exclude the 3rd cat if you want, as there are no sensors on it. Slightly louder maybe but 24" of straight pipe is much cheaper than the 3rd cat.
My Jeep: 2001 Grand Cherokee Limited, 245/65R17 Falken Rocky Mountain ATS, K&N drop in air filter, Bilstein HD's. De-badged, eagle-eye LED Tails & LED 3rd brake light, Addco front and rear sway bars, Superchips tuned & TM snip, interior 6k LED's, Gen3 ccfl projectors with Volt 6k HID lows, akebono brake upgrade with R1 Concepts premium rotors.