Originally Posted by Miko226
It seems to be a fuel pump issue from what I read should I take off the jb4 before giving it to the dealer or does it not really matter and just turn back to stock tune??
I experienced something similar (except there wasn't really a noticeable difference in power) and it checked out to be a VANOS error.
It's one of the common problems with BMW vehicles (like the HPFP for the 335i's).
I took off my JB4 (used the clear-code function before uninstalling) and brought to dealership. They found out one of the exhaust camshaft solenoid or something needed to be replaced.
My car has been in the dealership under warranty repair for over a month now (they wanted to replace a few other parts that are linked so I didn't complain).
My error code was P0015: B Camshaft Position-Timing Over-Retarded B1.