Hello everyone! I am new here (the forum that is!) and been having exactly the same problem with my g40! Mine has an m45 conversion and i had that same problem from the moment the Eaton went in! I later found out that the metal ring that goes to the end of the plastic pipe (last hose before the throttle, had slipped from its original position and had been stuck just before the sensor (the one that goes in with just a pin and is square looking don't really know what it does, guesting its an air flow meeter!) that was causing it to really give me a hard time when trying to start the car and did stall and die on every junction, since i got the ring out and clean the sensor with some alcohol everything got better! Now it only stalls only occasionally an only dies ones in a wile! Not totally cured but better anyways! The power came back that's for sure! I hope I have helped and would really like to know if you find out what is really wrong! (Sorry for my English as I am from Greece!)
PS: I did try to set the idle by the screw, before I find out about the ring and might have messed it up a bit, maybe the reason why it still stalls a little bit!