Retrofitted Cummins ISX with E

Hi everybody. I have problem with my Volvo powered with Cummins ISX EGR. I bough it in 06' model 07' unfortunatelly enigmę 06'. Not good for CARB rules. In 13' just before I retrofitted my rig I needed to overhaul the engine (600k miles only) due to broken valve and destroyed cylinder head. DPF filters been installed. They need to be serviced every 60k miles or every year whichever comes first. First service (vacuuming and baking them) I did after 57k and they were super clean!!! On the middle of next cycle I had problem with fuel system, loosing power on low RPM's and jumping. I went to cummins service and they figured I need new EGR plus all fuel pump selenoids. Had no way out so I paid for. On top they found broken fuel line (it was the main problem of course but aa always they start with big things not small ones). Problem resolved but I start smelling smoke in my cab trough vents and decreased fuel economy so I went back and they decided to calibrate ECU. Uploading, downloading and erasing data. Let's say I was satisfied. But next cycle for DPF shortened to 42k. Next one was only 21k miles. Shop manager said my engine is bad. They took filters down and performed opacity test. Results been great, only 3.6%. So they decided I need to go and do DYNO test. My truck runs great, turbo works smooth and silent (only noise I hear is pleasurable to ears "weeeez") does not take oil and only quarter of a gallon of coolant every 12-15k miles. Takes diesel
Results of the DYNO:
DYNO test truck, perform snap idle test before DYNO run and 5.6 percent opacity observed. Under load the smoke was so minimal that we could not get a reading on the opacity meter. Blow-by is at minimum no signs of smoking out of exhaust, did find that the turbo hot housing is glowing red under full load. Turbo is not working correctly and needs to be replaced. Also found exhaust leaking at manifold. Engine runs good.
I am not sure if the test was done the right way. How come on idling they were able to get reading on the meter and under full load-not? Where the smoke/hot air went? What can cause building up the sood in the filters if no smoke been observed?
Replacing turbo is easy, "only" 3-3.5k $'s but is this the problem of the sood buildup? How come turbo needs to be replaced if it runs great, silent, no weird noises and turbo boost gauge shows quick respond to releasing or decreasing on accelerate pedal.
Any ideas, advices or similar experiences? I am lost between shop mechanics directions.
Help.
Thank you

 

Thank you for advice. I will stop in friendly shop. They never ripped me of money so I trust them. I will ask them to check the EGR cooler. But do you really think small amount of coolant can cause so quick sood buildup in DPF? It's "passive" DPF system- it's uses hot air/smoke produced by engine to burn the sood in filters. Also my pyro gouge is not working since I stopped I cummins service last year. Can it give wrong/false info to ECU and cause it to mess with my turbo/exhaust system? According to DYNO test shop there is not enough of smoke to be tested under full load run so are they stupid or the smoke goes somewhere else? (????)
Last question, if high exhaust gas pressure will be corrected will it help to burn/clean the filters under normal duty?
Thank you in advance for help.