hello everyone i have a 2003 sonoma zq8 with just a hypertech,k&n fipk and no cat but my question is i have been running the spark plug fouler mod for my rear o2 sensor for about 2 months now with no dtc showing for the rear sensor so thats good but i have just recently got the codes (172)fuel trim system rich bank 1,(175) fuel trim system rich bank 2 and last but not least a (420) catalyst system low efficency. ok can someone please tell me what these codes mean and if i should really worry about them i really really do appreciate feedback thanks so much

 

You need to get the codes tuned out or put a cat back on it