I've been having a problem with the carb on my Bolens QT16. It has a 16 horse Onan BF twin. I believe the low speed circut is plugged up on the carb. While running a high speed it's OK, but I have to add choke as I idle down or it will stumble and stall. The low speed needle makes no difference at all. the passage from the carb throat to the needle is clear and from the backside of the needle to the top of the carb casting is clear. I'm not too sure what feeds this circut from there. So I guess my question is what is your favorite carb cleaner/method to use for a plugged up internal passage.