Ak Snowman, I suggest you inform yourself about snowmachines before making false comments. If the 4 stroke snowmachines (do you know what a snowmachine is or are you still in New York city?) are that much cleaner, then why do the ski doo etecs have lower emissions (fyi they are 2 stoke)? The epa sets emission standards and all manufacturers  meet current standards. Also, Can you cite a report that that shows an increase of emissions from an aftermarket exhaust? Or are you just against the noise? You do realize that the jet you fly on from New York city emits more emissions that 100 snowmachines do in a year right? Lets focus on big picture items not go after the little guy because you don't like them....