2000 1.8T ATW:

Previous owner had a new turbo put in 3k miles ago, along with all the fittings (or so the paperwork says) but ever since I purchased the car I can see it having a perfect vacuum (-23 I believe?) but a typical 3 mile stretch of racing around the city like a madman produces at max +4lbs of boost.

No other CEL at the moment (this was before I changed plugs, coils and vacuum line)

Boost leak test is next week but I wanted to start vetting items. What would be next to check?

 

Did you get an actual boost gauge or are you still using the app on your phone?

What about VCDS? These are two crucial tools for helping to fix your low boost.

 

Found out the MAF sensor was broken.

When I say broken, I mean that the silver diode was actually MISSING.
$60 later I replaced it, reset the ECU and the car is running amazing. Boost is back to normal, or so says the app ;-)

Ty for helping me through it.