why would gas be coming from the throttle housing that connects to the air filter housing?

i took my 2005 chevy impala in to find out why the check engine light was on and i was givin a p0300 code multiple mis-fire..my car rides terrible on take off and i have to press down on the gas to start it...while driving i have to put it in nuetral when i come to a stop to keep it from shutting off..so i decided to check the injectors and once i lifted the plate up gas poured from the housing could that be a bad pressure regulator or bad fuel injectors..can you please shed some light on this matter for me..respectfully eddie murry