Alright boys, i need some help, all will be appreciated
I have a 2001 Audi a4 1.8t AWM quattro

The problem is i think im in limp mode. Maximum 4-5 psi boost. It is not throwing any codes. Bought the car like this now i want to fix it.

Things I've done:
Cat has been hollowed for the time being because looked clogged but was not
Bypassed the N249 system
Did the suction jet pump delete as it was leaking badly
Did the PCV refresh as it was leaking as well
Checked the wastegate flap and looked to be in good shape

There may be one or more things but i cant think of them right now. As a note the turbo is spooling i can hear it through the now overly loud straight piped exhaust.
I'm getting down to the n75 thought this doesn't seem to be the proper diagnosis, or the MAF which i also believe to be wrong. Could also be another boost leak but when i tested it with a fogger i only found the two leaks (pcv and sjp)
I've also heard that the ecu relay goes sometimes? I find it hard to believe it wouldn't throw a code. Is this a common occurrence?
Any help would be greatly appreciated. Im a mechanic but have little experience with VW/Audi's.

 

I have the same car, but mine's FWD.

I can't think of a single thing that would cause that and not throw a VAG code (you are checking VAG codes, right?).

I can PM you a list of everything I've done to my car since I've owned it and perhaps there may be some random information in there that you can use.

I was the same when I bought my AWM also. Lots of mechanical experience and tools, but as we all know VW/Audi aren't your run of the mill engineered cars.

 

So i have a launch scanner, as well as a snap-on scanner, and another top end launch scanner i've been using. I assume these would scan all codes. Is there a secondary system that only VAG can read? if so i will purchase said scanner tonight.

 

Cat has been hollowed out and not throwing any codes? Something is wrong here, as there should be a cat efficiency code, which is OBDll and any scan tool will find.
Where an Audi scan tool (VAG-COM aka VCDS) would be beneficial is that software allows you to actuate various ECU-controlled parts from your computer, such as the N75 valve. That will prove whether or not the electrical circuit is OK.

 

i can do these controls with my launch system (they backwards engineer their systems to do most factory functions) but i will pick up a VAG-COM as well. Ya i thought it was odd that it didn't throw any codes after i hollowed out the cat but there are no codes thrown for it. I find all of this to be kind of odd, and when its making boost its 4-5 psi max does not spike above or drop in top rpm(which kinda makes sence) and which is why i believe it to be in limp mode. but I've fixed all the things i think relevant to boost and limp mode (minus the n75 valve which is on the way). Seriously though any help would be greatly appreciated.

 

Ok. So im fairly sure its the n75...

 

Let me know if that works.

 

and after all that...of course it ends up being the n75....and while testing my new found boost (uni stage 2 tuned) i end up buzzing a cop...while being unplated. 800 bucks later my car is all fixed.