i just changed my whole system to a warp-speed y pipe wit a magnaflow cat and a stillen axle back and now i got a CEL saying (from autozone free OBD2 scan)

code:P0420- the PCM has determined that the catalyst system efficiency for bank 1 is below threshold for the current engine operating conditions.
Definition:Catalyst efficiency low bank 1

so does this mean i have to go back to the stock y pipe with the 2 pre-cats? please help me out guys its been a year with out state inspection lol. i dont kno how much longer i can get away with that.

 

It means you need a stock cat, probably, but I have also seen that code more than once caused by bad o2 sensors.

Oh, and this is the classifieds section