First swap the EGR-N75 back. I don't think this is causing your problem though.
The MAF is probably fine from your rough test.
If the VNT LEVER moves easily by hand when the rod is off then the vanes are fine.
If the rod is the same length and starts to move around 3, the VNT actuator is fine. You have now ruled out the turbo and actuator.
If you stomp on the gas pedal some small spikes in manifold pressure actual vs. requested are normal. If you drive smoothly they should stay relatively close. If they are not, you know the problem is most likely related to the turbo control.
Possible problem: bad manifold pressure sensor - this is unlikely.
Bad wires to the N75 - more likely. Bad N75 - more likely. Bad vacuum line somewhere - more likely. My guess is that a vacuum line was bad, by disturbing it, the hole or defect is getting worse. Even if it looks fine, replace the lines going to and from the N75.
When you tested the VNT actuator, did it hold vacuum? Did you use the same line that is on the car? If not, this is probably the problem. I say replace the lines anyways since they're cheap, probably worn out, and more likely than other causes. Inspect all the vacuum lines back to the black vacuum bulb and to the vacuum pump at the driver's side camshaft.
As a last resort, the ECU could be bad, this is unlikely.
The MAF is probably fine from your rough test.
If the VNT LEVER moves easily by hand when the rod is off then the vanes are fine.
If the rod is the same length and starts to move around 3, the VNT actuator is fine. You have now ruled out the turbo and actuator.
If you stomp on the gas pedal some small spikes in manifold pressure actual vs. requested are normal. If you drive smoothly they should stay relatively close. If they are not, you know the problem is most likely related to the turbo control.
Possible problem: bad manifold pressure sensor - this is unlikely.
Bad wires to the N75 - more likely. Bad N75 - more likely. Bad vacuum line somewhere - more likely. My guess is that a vacuum line was bad, by disturbing it, the hole or defect is getting worse. Even if it looks fine, replace the lines going to and from the N75.
When you tested the VNT actuator, did it hold vacuum? Did you use the same line that is on the car? If not, this is probably the problem. I say replace the lines anyways since they're cheap, probably worn out, and more likely than other causes. Inspect all the vacuum lines back to the black vacuum bulb and to the vacuum pump at the driver's side camshaft.
As a last resort, the ECU could be bad, this is unlikely.
