i have been doing alot of search about the air fuel when accelerating,at idle,crusing,and boosting but what i have not found is what about downshifting or letting the motor slow the car down .. my guage always goes full lean then does this(--) im guessing it has to do with a fuel cut or something but what i want to know is this ok to happen since the car isnt under a load for it to be full lean like that...

 

Decel fuel cut. Supposed to happen.

 

so its not harmfull what so ever.. thanks.

 

It's Fine
Dave

 

just think of it as the car doesn't need any fuel to slow down.It can do that on it's own.
It just needs gas to speed up!