ISX cm2350 low. power/poor. Fuel milage.

[DPS567180]

Okay. Life has been kind of crazy but I finally got around to taking care of some of these things. I took the decomp tube off And man it was pretty bad I cleaned it out really good as best as I could I was afraid to pressure wash it so I just kept using a hot water and pouring through it and wiping it out. Installed new injector also changed all EGR cooler I found it was leaking internally so glad I caught that before it got too bad and now the truck pulls a lot better but nowhere where it should be when pulling hills. Boost is still around 28 to 30 tops when on a long pull no matter the weight. I was just coming back to Vegas from salt lake with a 11,000 lb load And I couldn't get over 50 mph on those hills. I still have no codes. I can still hear a whistling noise too especially when using my engine brakes. I'm suspecting my actuator or EGR valve but then again I'm not a professional any suggestions on how to narrow it down?