During the winter my heater would slowly get colder and colder as I stopped at lights, drive-thru's, etc. I never noticed an issue when I left my car out to heat, only when stopped. If I even got above 15 or 20mph I would get heat again. This makes me believe it is a problem with suction, or maybe a hole somewhere where pressure is lost. Has anyone else had this issue?

I'm also noticing now the car sounds 'air-ee' when driving, like air blowing out of hose. Are there at least any good methods to finding the problem?