96 disco failed smog

[yoeman]

My 96 disco 4.0 failed smog due to high NOX All codes are cleared New plugs ngk bpr5ey, coolant temp sensor and injector cleaner but still no luck It seems to run rich on start up and rally gulps the gas My shop wants to change the cats for $1500 plus but im not convinced yet Any ideas

 

[sammy]

Try replacing O2 sensors, or try a product called "Guaranteed To Pass", it works.