Turbo surge cold idle

[Justinotruckin]

I recently purchased a truck that was already de mandated When first started it will turbo surge excessively enough to shake whole truck for a few mins then it seems to kick out of that mode and does fine there after. It does this pretty much anytime it is shutoff a few mins and restarted. Also it has no 3rd stage of Jake at all. I can flip switch from 2 to 3 and makes zero difference. Pretty sure it’s all in the tune or could possibly be the turbo or actuator sticking but has no codes or cel. Other wise runs ok. Fuel mileage seems to run 5.5 to 6mpg but live in area with a lot of hard pulling in mountains and run heavy. Is it normal on these 2250 to lose the exhaust brake if Jake with a demandate or is this a sign of crap tune as well? I’ve been in trucking several years but mostly cats older Cummins Detroit’s etc. this is my first isx The engine is a cm2250 isx 450st cpl 3719 Thanks