Ever figure this issue out?
I'm having a similar issue with my 2012 MKS. I noticed it feeling slower, so hooked up my boost gauge. I'm hitting a max of 11psi with a 3 bar tune installed, 2 bar tune installed, and returned to stock. I don't hear any weird noises, but it seems something is holding me at 11psi. No codes and car is operating completely normal, other than feeling slow.