Car keeps stalling
 

Hey there have Charger 2006 5.7 Hemi that I recently installed a new engine. The car continuously keeps stalling at lights and on the expressway. The mechanic that installed the engine says the engine is mechanically sound that it's possibly a computer board issue either from the engine or the transmission. I took it to the dealer and had them reprogram the engine computer but the car keeps stalling. The company I bought the engine from told me to do a cylinder leak down and to check the compression which the mechanic did and found no problems it passed the test. Does anybody have a clue why this is happening