Having a rough time trying to figure out what's going on here.  The car is an 01 A4 1.8t RallyCross car.  Its gutted of most everything inside.  Car had run great for a long time but recently has developed an issue only boosting to wastegate actuator spring pressure.  I noticed it after logging my last event.  Part of what's making diagnosis difficult is that there is no ignition key so I remove the battery between events.

Logging the ECU it is calling for 18 psi and 95% wgdc.
You
So far I have:
Replaced the N75 and found identical results
Driven with the feed line to the wastegate actuator disconnected and partial throttle and got up to 17 psi.
Replaced the primary O2 sensor
Checked for boost leaks
Repaired a pcv leak
Replaced the ECU

At my N75 location I'm recieving 12v on the supply and have 3.5v on the ECU connection to ground.  On the fuel pump relay trigger leg I have the same 12v on the hot and 3.5v on the ECU side.

Is there another variable in the ECU that can be overriding the wgdc in limp mode like the lambda variables will always use the lowest one?
Is there something else that I need to chase?
Thanks for any help.

Got it fixed.  Partial ECU failure.  N75 was working fine.

I didn't realize that it was correct for there to be voltage on the ECU line where it supplies ground.  I had assumed that there would be 0 voltage between the ECU and the ground at the n75.  After I changed the ECU I checked the voltage and it was still there, so I assumed it wasn't fixed.  Test drove it later and it was.