I heard that i would be able to replace my cat with a test pipe and disconnect the secondary o2 sensor without it throwing a check engine light, but that would be with a mugen ECU. I was wondering if i would be able to do the same thing with running the stock ECU. Im running an 01 GS-R.

 

no that couldn't be done with a stock ecu..your car will most likely barely move with that second O2 sensor out