Originally Posted by Gugs
They do. Poster above is incorrect. And as per Terry it's better to Remove the down pipe fix rather than to just leave it in as the Jb4 does a better job. The dpfix is usually just for inspection with jb4 disabled and should be removed after.
JB4 simply clears the DP codes.
You can leave the BMS DPFix in place and turn off code autoclearing and drive, plenty of people have the DPFix installed year round. I haven't seen Terry make any statement that you shouldn't have the DPFix in, feel free to link it.
2009 E90 335i - All go, no show
Mr. 5 Intake, VRSF DP, VRSF FMIC, Quaife LSD, BMW PS, M3 Bits, RE Toes, ER CP, Forge DV, Cobb AP/JB4, PSS