It sounds like you may or may not have a few different issues. With the information you've given us, it's almost impossible to diagnose to use the Internet.

Your best bet would probably be to find someone you trust to look the car over.

 

Sounds like your fuel pump is playing catch-up or its seeing some knock and pulling timing logs from evoscan would tell you for sure.

 

Have you done an actual boost leak test? Your turbo will still hit target boost when you have a boost leak, it will just work 2,3 5 times harder and blow out hot air that is lousy for making power.

 

It's funny how op's tuner has nothing to say about it.