My car was also doing this I was getting around 40-70hg at idle when it should be between 18-22 hg at idle. (not sure how different with a mild tune.) Under load it was going to 100-130hg, I do believe. You can also see in the data log I am boosting at 100-115 PSI. I had replaced the MAP sensor and cleaned all the sensors and that didn't work I tried looking for all kind of leaks and found nothing then I found that the cracks were a bit bigger then normal in my turbo exhaust housing and the waste gate pin was sticking. I would defiantly look into this. Go check out what my turbo looked and sounded like there's picture and a video here. https://www.cruzetalk.com/forum/34-g...ake-turbo.html
Also if you can download EFIlive, I'll add my data log of when the car was acting up and you can see the MAP sensor is way off also the long term and short term fuel trims were off but I don't know if I caught that in this log or not. I was getting codes for a lean condition then it switch to a rich condition. Do you know if spark plug gap being off could cause lean or rich conditions? I came to the conclusion that this was the issue because I was getting codes for rich and lean conditions at different time so I am thinking this was either when the wastegate was sticking open or sticking closed. Also I have a 2014 1LT with Auto trans. My car was also falling flat on it's face in higher gears and rpms then started getting a surging/chugging idle.
I wasn't sure how to get the .efi file on here so I just used mediafire if you'd like to view this can download it here https://www.mediafire.com/file/rp2ez..._0045.efi/file and you will need the EFIlive and can get it here, EFILive - The Latest - Download EFILive . I would suggest taking a look at your wastegate pin.