I notice when i am crusing at neutral my idle fluctuates from 300 to 500 rpm. Is that normal. One day driving to work going downhill put it in neutral rpm drops really low until my engine dies . Does anybody experience this

 

I did for a little while when I started tuning, but once I got my afr correct, there was no longer any issue. Do you have this problem when you're idling at a stop? Any codes popping up?

 

I dont have a problem idling at stop my only issue is when the car is moving in neutral position the idle drops at 300 rpm. For example i am approaching a stop light or slowing down . I put it in neutral and let the car roll . Or when going downhill in neutral my idle drops.
I have no engine light , no unnecessary noise, my clutch works fine, everything is stock no modification.
What do you mean by afr?