Brief puff of white smoke on highway

International 9200i C15 475HP for the last few days, every so often on the highway (mostly hills) the truck will bog out or become sluggish and let off a medium cloud of white smoke. It happens very quickly and then it's back to running normal again. Almost never happens during local driving. Strictly at higher speeds and I could be imagining this but it seems like hills make it worst. Any clues as to what this can be?

 

Hey guys, thanks for helping out. Just left the shop and it turned out to just be a really dirty water separator fuel filter. Thank goodness! I had them out my injectors on the computer just for my piece of mind and they are fine. Lucky me. I will sleep good tonight.