Stalling on overrun
 

My first question so be gentle. I have an 85' Euro with a SW chip that I just picked up last week. I am having a problem with the car stalling when coming off the gas. It happens consistently when the car is cold and intermittently when warm. I have noticed that no matter what the revs drop below 400 whether the car is cold or warm for a second before bouncing back up to ~850 which is normal idle. The car does idle fine and this only occurs if the car is given gas. I have searched for a while and not found anything related.

TIA,
MO

I have a couple of ideas, but some others may be able to narrow it down a little better.
This is based on my similar problem that got worse when the days got colder, although I did not have the problems you have when it was warm.

Check to see that the Idle Control Valve (ICV) is working. Turn the key to just before start and put your hand on it to see if you can feel any vibration.
Make sure your (Idle) micro switch on the throttle body (TB) is working.
Check or replace the cylinder head temp sensor (CHT).
Check for intake air / vacuum leaks.
O2 sensor acting up(?).

If you have a Bentley manual, it can help with the above steps, otherwise, write back.

I hope this helps to get you started.