I have a 2004 IC BE series bus with 8 cylinder engine . The bus has over 160000 miles on her . A driver walked behind the bus and told my supervisor how strong the exhaust smell was . We have had issues with leaking exhaust into the bus and fixed that . There is no smoke of any kind but it does smell and can't tell exactly what I smell So any ideas . I am just wondering if the engine is just wore out . We did have EGR coolers go bad and replaced those along with the turbo .