Car stalling at idle

Problem started 6 months ago or so, when car comes to a stop it would hesitate and die or if I tap the gas pedal quickly I can get it to go. It was running fine for a while but it is doing it again more often. It is stalling about 3-4 times a day at random it does not do it most of the time, you never know when it will happen. If I come to a stop and brake with left foot and put right foot on gas to increase idle it will not die. When it does stall it is hard to restart like engine is flooded have to rev up engine and pop it into drive to go it is rough at beginning but seems fine when moving, at speed seems ok. I have replaced the idle speed control valve(with a used unit that was tested good?)Any help would be appreciated Thanks.