I have a b&s 9hp intek motor on a troy built 33" walk behind mower. The issue I have is that I am getting a backfire out of the carb and surging when the engine is run without choke. With the choke I can usually find the sweet spot by slowly applying choke until it stops backfiring. I have tried numerous things from people with suggestions to issues similar to mine. I have cleaned / replaced the carb with 0 improvement, check for vacuum leaks post carb by spraying choke cleaner around the seals with the engine running, check that the valves were opening and closing as well as adjust them, gapped the spark plug and the magneto. This is all with fresh gas. I thought the engine was running lean but when I spray a little bit of choke cleaner in the carb it chokes the engine out immediately so I think maybe its running too rich? I am kind of at a loss here and don't want to try just replacing multiple parts just in the hopes that I get lucky and find the issue. Any help would be a god send. Thanks!