husqvarna lawmower won't idle

Hello all. I have a husqvarna lawn mower model HU775h with a briggs stratton engine. At first it began with idling issues so i removed the carb, cleaned it out but issue remains. I went ahead and bought a new carb and same issue. What I am noticing is that it will not idle with the air filter housing on. If I remove the air filter housing it works just fine. Any recommendations on what else it can be? Thanks

I just walked into the garage and smelled a large gasoline smell. Walked over to the lawnmower and found that it was leaking from the muffler and a puddle of gas below. I went ahead and removed the gas line and emptied out the muffler as well as the carb. What would be causing it to continue flowing gasoline even while off? Could this be part of the issue?

Either the float valve on the new carb isn't shutting off the fuel flow, and the carb is overflowing. Or for some reason the air vent for the carb bowl is blocked and is creating a syphoning effect. Some carbs vent through a hole in the mounting flange of the carb, through a hole in the air filter mounting plate. if the gasket gets incorrectly installed can block that vent hole.