I have a 2001 xj sport utility. And my catalytic converter was stolen and I picked up a flow master cat to replace it. I did the welding my self but I'm not sure if I have an O2 sensor after the cat. They cut a lot of it out, but my jeep has no check engine light and I don't see any cut cables where an O2 sensor would go. Nor am I getting and codes at all.

Side note I'm having trouble with my xj misfiring (not sure if it's related) but I have all new spark plugs and coil packs, new 12 port fuel injectors, and my compression is good, but I'm still misfiring occasionally. And some days I have nice throttle response and high low end power. The other days the throttle response is lagging, and feel like the Jeep has lost a significant amount of power. And has a low, rough idle on start but sometimes will start perfect and sit smooth.

I have a hunch its the wiring harness for the missfire and have new fuel injector plugs just haven't had time to make a new harness
Current mods:
SYE
3" lift rough country
New more powerful battery
12 port injectors
Sparkplugs, and coils
High flow cat
Throttle body spacer

 

Have you checked the fuel pressure ? and fuel pump relay ?

 

No I have not, I'll will check that. Ty