The after cat sensors are measuring the effectivity of the cats, so if you cut the cats out, you will get the check engine light and the fault code for cat efficiency. An O2 sensor simulator could get rid of the code, but most probably is an ilegal fix.
JEEP Grand Cherokee 4.7 Lmtd 2004
HID 8000K in low and fog / Quad Squad member
KYB Gas-a-Just shocks / Pirelli Scorpion ATR 245/65/17 - Transgo reprogramming shiftkit.