Just put on a pair of shorty slashed, no baffle pipes on my 2007 Speedmaster. It sounds good, a little loud but OK. I am now getting some backfiring when shifting or throttle off. I know they say you should re-jet the carbs when you remove the baffle or change to open pipes, but would the lack of re-jetting create a backfire, or is it just that the back pressure is not being caught, re-distributed due to the open pipes? Thanks.