car stalls when stopping on a red light or waiting to turn on a stop sign on 2001 BMW 325Ci

after driving on a highway and exited, when i stopped on a red light, the idle speed dropped and the engine stalled. This happened twice. Also when i was driving on a highway and hit rubbernecking traffic, the engine stalled. My nephew who used to work at BMW dealership checked the disa-valve and the fuel fuse which are good. He suggest to replace the idler control valve but it is very expensive. May i know if we are on the right track, or is there any other underlying problem. Please let me know and thank you so much.

Asked by for the 2001 BMW 325Ci
you need to find a reputable BMW specialty shop that can diagnose this for you. without proper software or diagnostic tools, you're just guessing on what's wrong.