It all depends on how the question was asked.
Are you in favor of all gun sales being subject to a backgound check even if that ment regeristering firearms?
I'm guessing 72% of people would say yes.
Are you in favor of gun registration so the government can confiscate guns in the future?
I'd quessing that 90% of people would say no.
FYI - lots of my non-gun owning friends think that all guns are registered now. It's often difficult to explain that they are not registered. Many also think that is easy for the government to track gun ownership. They don't understand the FFL sales record system or the difficulty in tracking a gun sold 20 years ago.