That roots blown EMD 567BC or 567C or even a 645 could never comply to tier zero let alone tier 4. My guess is that they needed better air filtration. The Air filters are right above the main gen on either side of the auxilliary generator, it looks like thats where the piping goes. Randy
Seriously, it appears the train works a rather grimy area. So, could it be the aircleaners are for the crew as well. Aanother question. What is that red thing by the front wheel?