Strange boost problem!


Apr 26, 2018
335i N54 2006
Hi everyone, strange issues with the 335i!

Car is a 2006 RHD N54 335i with DP, intercooler, BOV, Charge pipe, Inlets, Outlets and RB Ones, JB4 (G4) Curently Map 2 (14.5 psi).

I have been having some issues with making boost. Most of the time the car will spool up no issue hit the 14.5psi, car feels solid. When its not working it only spools up to 8-9psi, feels slightly faster than stock but slower no dougbt!

Whats strange is switching maps on the jb4 when only hitting 8psi, makes no difference. Unless setting map 0 when the car only seams to make 2-3 psi.

Jb4 was removed same test again and while I had no boost indaction you could tell from the sound of bov/inlets + reduced power, when the car is running stock boost or reduced 2-3psi.

Whats strange is there is no EML or 'Reduced power warning'.

All the vacum lines have recently been replaced and did not make any change.

I will try and post a log later of the issue as long as my data cable turns up in the post. Thats asuming the car wants to flag the fault up tonight!

Any help is greatly appreciated :D