Originally Posted by Tee-Dub
Not true, the JB4 just auto-clears any codes that come up. BMS does sell an O2 simulator that you can use to fool the ecu (and any OBDII tests) into thinking everything is ok and you can use it with the JB4.
"The JB4 tuning system includes this functionality built in so a DPFIX is not required if you are already running a JB4 Performance Tuner!"
Taken from their site...