TIP: Check your sensor plate
 

I'd been having a nagging problem for the last few months. When releasing the throttle back to idle (sometimes quickly, sometimes slowly) the engine oftew died.
Tried changing the mix, idle, pressure on the decel valve, but nothing fixed the problem.

Last week I removed the whole CIS setup to fix some minor leaks underneath.
While there, I noticed that the sensor plate was not correctly level with the narrowest part of the funnel, so I adjusted it.

After getting everything together, the idle problem was gone. Now, it's stable and it never died again. I think the culprit was really the plate position. Don't forget to check it.