87 dies in reverse when at operating temp.

my 87 kills when i back up.. (350 TBI 1/2 ton) I changed a fuel pump recently and the ECM. there is a new Idle control Valve and EGR valve in it. It also kills when I am braking to a stop. Seems to happen most often when the vehicle is at operating temp. I am going to check all the vacuum lines and see if there is a crack or weak point. this problem did not exist before the fuel pump was replaced. Some times when I walk by the fueling area I can smell gas. Do you think I have a kinked line and the tank is not getting air and that shuts down the pump? thanks for any advice that you can bestow on me. Engine is brand new as of January.