Odd JB4 issue - boost target 0, DME boost request ~ 4psi


Jul 27, 2017
Hi Guys,
I have a strange issue where the ECU_PSI is higher than the JB4 target boost.

This is occurring on around 20% throttle and low RPMs.

The ECU_PSI will sometimes go as high as 4 psi while the JB4 target is 0 but usually it's around 2 psi.
I think this is causing my fuel trims to max out, lean as theres way more air than the car is expecting.
If I give the car more throttle then the jb4 target boost increases and trims go back to a normal range. Even slightly rich, witholding fuel.
I am running the pump back end flash. JB4, hybrid turbos, 540lpfp, inlets, outlets.
I presume the flash is driving the low end boost request and I must adapt it down to avoid this lean situation?
I have raised fuel scalars in the flash to account for using hybrid turbos and ~93 octane pump fuel.

Would adjusting the spring on my wastegate have any effect? I'm guessing not as the car is requesting x psi and getting it, while the JB4 is not requesting boost.
I thought the JB4 would always request at least as much boost as ECU_PSI, if not more.

Thanks for any help and advice


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