Hello everyone,

I’ve been struggling for several months with my 406 2.2 HDi; it goes into limp mode during hard acceleration, specifically under full turbo load.

Current setup:
- Stage 1 (2.4b boost)
- EGR, DPF (physically and in the ECU), and catalytic converter, removed --> no ECUsafe
- 60mm downpipe (custom-made using a 406 2.0 HDi catalytic converter)
- Smoke by MAP

Here are the DTCs :
- P1421 : upstream catalytic converter temperature sensor --> since DPF removal, even after setting the number of sensors to 0, I can't get rid of it.
- P0235 : MAP sensor issue --> logs show no SVBL (2,5b) exceeding. That's the maximum value the sensor can handle, but it should still work.
- P0245 : boost pressure too high / N75 valve issue / mass airflow sensor out of range --> Idk
In general, P0235 and P0245 do not appear simultaneously; one or the other is triggered when it switches to limp mode.

I haven't modified the N75; it seems too complicated to me. I modified underboost/overboost tolerance but that doesn't solve the problem.
The turbo is a year old, so I hope it's not the variable geometry mechanism that's seized up—I really don't want it to be the geometry.
Why would it be when I'm running an AFR of at least 15, while tuned TDI locomotive have their VGTs working perfectly with half my AFR ?

I also modified the vacuum circuit (removed all EGR and throttle body hoses), but when I disconnect the N75 valves of the throttle body, two DTC pop up :
- P1402 : EGR issue
- P1451 : throttle body control issue

I have a DAMOS for Citroën C8 2.0 HDi containing singles ​​that could potentially prevent throttle body DTCs from triggering, but I can't find them in my dump. Is there a DAMOS file available for 4HX ?
I'm thinking of ditching the vacuum reservoir and connecting the swirl and turbo valves directly to vacuum pump.

Thank you in advance for your help.