High Fuel Rail Pressure with Low Boost Pressure

I have a 2012 Pro Star with Maxx Force 13. It lost power this past weekend. Boost gage won’t go over 20psi when engine is hot. I changed both fuel filtes and it ran great 40 psi boost pressure for about 3 or 4 miles then back down to 20 psi. When I parked the high exhust temp light was on. DPF system is fine did a forced regeneration anyway soot level was at 54% and dropped down to 20%. It has codes 3055 and 3055-17 and a low boost pressure code. Forgot the number.
Any help would be greatly appreciated.
Thanks
Fedexbob

 

Ok thanks, I’ll change the filters again
And see if there is any sign of water.

 

I don’t think so unless it was factory installed. I never added one. I had to google it to see what it was. I’ll check it out. What problem would that csuse if I do have a DAVCO system.
Thanks

 

I’ll check the back pressure plate.
I dropped the truck off at a Freightliner dealership. They can’t figure it out. They said they don’t have the diagnostic tools to determine whats wrong with it.
The local International dealer is booking 4 weeks out. Can’t get the truck in to be looked at until end of May. Freightliner mechanic says low pressure fuel pump is fine but can’t tell about the high pressure side but did say it was kind of noisy.
Thanks