my fd began to run lean over 4000rpm sometimes and now permanently.

When part throttle at low revs, it fluctuates kindly around 14.7 afr.
When I floor it, it enriches progressively to 12.5, but after 4000rpm it drops to 17 Afr and more. I can't tell what happens after because I immediately cut to protect engine.
It seems to be real lean conditions and not an exhaust leak before wideband sensor because narrow band sensor at stock location even switches poor after 4000 rpm. Before this problem I had solid 11.2 afr past 4000 to 8000.

Boost is 11psi
Turbos are full parallel
Pump is hardwired throuth 30amp fuse.
Ecu is stock.
Jdm downpipe, straight midpippe, catback and air pump disabled.

Tested secondary injectors.
Injectors grounds continuity to ecu harness plug OK
Injectors 12v continuity to battery when power on OK
Injectors are both 14.2 ohm
Injectors both clicks with 9v battery stimulation. I can hear spray when fuel lines are in pressure.

I dont know what more to test.
Do you have any ideas?

 

Most probably your ECU.

 

Precision: ecu is stock remapped for the mods listed and 13.5 psi. And as written, I used to have 11.2 afr at 11psi on boost before. And recently it turned lean.

 

Have you checked all the turbo components to see if they are all running correctly.
Running a full exhaust on stock turbos from what I read is risky as you can get some boost creep, what psi are you getting after 4000rpm? If you never checked I would say rather not as if you AFR drops to 17 then you are headed for a blown motor in no time, maybe take it back to your tuner and have them look at it.

 

0.75bar peak dropping to 0,7.
But since the phenomenon happened I only use the car on vacuum range.

 

Sorted.

I did 2 things at the same time so I don't know the root cause but it was one of the two things:
- ultrasonic cleaned secondary injectors
- changed FPR

 

Sounds like it was your injectors, makes sense only starting at 4000RPM.
Could have been both, glad you sorted.