There is a difference between losing boost and going into Limp mode. When you are in limp mode, you will 100% throw an engine code and you will not be able to boost more than a couple psi.
If your fuel trims are bouncing, and you are having issues building/holding boost, but are not throwing a code, I would think you have an air leak somewhere.
I recently went through the exact same situation. Turns out I had 2 issues.
1. Someone replaced the 3 BAR sensor on my Driver side IC Pipe and did not install the Blue O-Ring which is the proper size for the hole in the IC Pipe. I fortunately had spares
2. My Passenger IC Pipe was slightly crushed from a T-Bolt Clamp being over tightened [My Fault while troubleshooting]
#2 was harder to find because that is where I was connecting my Boost Leak tester and I just happened to notice it was no longer round after I took the tester off.
I was still able to boost over 25PSI, but I could not hold it. Now my Boost and Airflow are a flat line until I shift.