I agree with Diablo. Venting to the fuse is ONE of the ways to deal with this situation. My opinion is that this is more of a gas engine carb thing, than a 3W thing. Other than the horn (which I like very much) seems like there are three ways to tune out the burble in gas carbs. The one Diablo mentions, the plate over the carb cover that 3W lists in their literature, and the tube soldered to the diaphram cover with a line to the carb venturi. That's the picture I've attached. I've had to try a couple of different methods depending on the engine/plane setup sometimes before I found the magic wand. Keep trying and it will work out_bob[img]