'07 565 ISX Cummins boost fluctuation

Howdy fellas. I have a question on the way my turbo boost has been responding on my 2007 565 ISX. It has a EGR but no DPF system.
Below normal operating temp and all the way up to temp I'll get 45-48 lbs of good solid boost with a steady pull. Once I get into the hills and really start exercising my engine my boost will start to fluctuate. I'll throttle into a hill and watch my boost come up to about 40 lbs and then hear it dump pressure through my exhaust. Once it does that it'll drop down to 33-37 lbs and my exhaust temp gets to about 950. It'll continue this even if I run my fan and bring oil and coolant temp down to normal. But once I hit flat ground and cruse for about 20 mins of normal running temp it will resolve itself and give me normal boost. Every once in a while (about once every 2000 miles) during a steady pull it'll throw a code PID# 411 and leave my check engine light on. I have to pull over and shut the truck off for a min and it'll clear itself. Anyone ever deal with similar or same issues before?

 

Fuel filters are new. Been doing this for a while now.

 

Thanks.