2005 lesabre flooding out

If it dies when you let off the gas, that can be due to a bad intake air control valve/circuit (IAC). Try cleaning that or replacing it. This would not be considered "flooding", which is not a real issue in modern cars. If, however, you feel the injectors need to be cleared of fuel, you can hold the gas pedal all the way to the floor during start (no need to pump it), this is called "wide open throttle" (WOT) and will tell the computer to not send fuel to injectors while engine is cranking. Your problem however really sounds more like the IAC than anything else.