Given the history of cracked exhaust manifolds on those Cummins engines , I'd say that would be the first place to check.
EDIT: If your traveling in Northern AB foothills , have you noticed any issues with fuel supply? Edmonton refinery problems have some stations running out.
99DSDP 3884, Freightliner, XC, CAT 3126B, 300 HP /ALLISON 3060
2000 Caravan toad, Remco & Blue Ox.