97 venture smart carb problem?

[jc2white]

I have a 97 venture 600, and am having some problems lately with it. It will run fine for about ten minutes, then it will get bogged down when under load (like up a hill, or in powder). Then it will back fire and the only way to get it home will be with the choke half on. It was taken to the dealer last year for the same problem twice and the carbs were cleaned and the sensors checked. Any suggestions; could this be a smart carb problem?

Thanks.