THIS is why i wanted you to post it here. 140g/s for a 180hp tune is low. A healthy 150hp must flow about 130g/s at redline, a healthy 180hp should flow 150g/s at redline. You might have a vacuum or boost leak, maybe a defective component somwhere... this is why you are having underboost issues and not reaching requested loads.

My car has reached 130g/s with 150hp tune, 152g/s with 180hp tune, and now I am flowing 164g/s at 5700rpm and 169g/s at 6300rpm. Which I believe to be the absolute reliable limit to stock k03 turbo.

To estimate power it is said through the internet to use maf reading/0.8 but I consider this calculation too optimistic as 130g/s would translate to 162hp. I use mafreading*1,2 which translates 130g/s to 156hp (more accurate on my perspective). Same for 180hp, do the maths. 169g/s*1,2 is 203hp, which I belive to be accurate when running against similar power/weight cars.

Smoke test your car and make a thorough check. Untill you don't get those values with stock tunes, do not tune any further.

Best regards.