Depends on too many factors to really nail it down to that one thing (depending on the setup)...but more of the cars I have tuned that have this issue are 8 lb flywheels

 

Have you turned the hot idle revlimit up past 1300? That was my problem with Trav-***' 1100cc, I could get it to idle sweet at 750 rpms, but it would stall on the decel part of the time because the 1100cc have the worst spray pattern in the world and couldn't atomise the fuel without significant airflow to break it up.