[r33_RGSport]

@AlexGT, may I know who told you that ER Catted downpipe won't throw CEL?
Because as their reseller and other brands, no one ever promised a non CEL catted downpipe.
High flow catted downpipe is a hit and miss on the CEL.
The main reason for catted downpipe is to reduce polution while still having a good exhaust flow.
But since most of the new car ECU are too smart and the smog center will fail you just because the CEL is on, catted downpipe is just to avoid the smell and makes you happier knowing that you are not contributing to the polution.
Also, on the clearing CEL through OBD2 port, with a module, some new smog test like what they have in Cali, will not let the car to be tested since the car is not primed. So you will have to drive the car for 25-50 miles before you can get it tested, which by then the CEL will goes back on.
Also, with all the new ECU design, every code clearing, means the ECU trying to relearn the engine to run optimized.
As for BMS JB4, it works differently, I believe it just intercepted the O2 sensors signal and alter it to avoid the CEL.