Exhaust Back Pressure at Idle . Turbo boost spiking

[BrandonOlsen]

X15 CM2350 X114B
Having exhaust back pressure at idle. Doesn’t matter if engines cold or hot. At 700 rpm it’s not very noticeable but you can hear the turbo boost intermittently. At 800 rpm boost goes up to 10. At 950 goes up to 20. When idle reaches 1000 it goes away. Seems as there is a rattle in the valve train (been the way since I bought the truck)

Engine has 660,000 miles. Rebuild at 590,000. Bought it at 640,000. New emissions during overhaul.
I just got insite and have done the rail leak test. 288 drop in 60 seconds. Did the cylinder cut out test and it passed. Just now did a forced regen to make sure it would complete one. Completed regen in about an hour. I have geo tab and it has been showing a constant active regen.
Insite shows no fault codes.
Parts I’ve replaced
Inlet Nox Sensor 11-16-22 due to code 3725
Air filter
Crankcase pressure sensor
Egr Differential Pressure sensor
Dpf differential pressure sensor
Exhaust gas pressure sensor
Intake manifold air pressure sensor

- from egr cooler inlet to the intake I took off all pipes and cleaned them with carb cleaner. I replaced the egr cooler inlet gasket, and all o rings and seals to the intake. Replaced all CAC hoses and clamps.

Exhaust outlet pipe replaced with Part # 5579020 when I first got the truck. 644233
Bellow pipe was replaced as it was leaking and sending smoke into the cab at 655,616

RIGHT NOW.
— after regen truck is idling on its own at 800rpm. Usually always idles on its own at 700. I always bump it up. So with the truck idling by itself at 800 I’m not getting the exhaust back pressure with turbo boost spiking. Bump it up to 900 and still doesn’t do it. No change at 1000rmp. Usually when it idles at 700rpm and I bump the cruise up 1 notch it goes up to 800. Now with it idling at 800, I bump it up 1 notch it only goes to 830.

What do I do next ? Is there a way I can send info from insite to someone to look it over to see if something’s out of line? Appreciate all the help I can get.

-This all started after I got the 3725 code-
I did send in an oil sample and it came back good