Bout the same time I bought my first diesel also Scott. They blame it on having to take out more sulphur than they used to. My truck doesn't smoke like my first one. Now I have a 2009 Dodge 3500, with more emission crap on it. I do know for a fact ExxonMobil built a unit in Baytown Tx and Baton Rouge La to help strip the sulphur . Cost a ton of money, but they won't lower the price, even though those projects have paid for themselves. I retired in BR from xom.