I'm trying to figure out why a K&N filter would cause the car to pull fuel out when it should be seeing more air flow? Unless my understanding of how fuel trims work is flawed ??? A negative trim means the car is taking fuel away in order to meet commanded AFR right?
Anyone have a theory on this ??

With the stock filter the cars trim's are a perfect 0. Please enlighten me if you will ....thanks.

 

Yes, a negative fuel trim means that the car is running rich and the O2 sensors sense that and tell the injectors to spray less fuel. If you remove the airfilter the fuel trims go even more negative. I believe it has to do with turbulance at the MAF. Because even with a stock intake with no filter the LTFT goes to -9 on my car. It is -4 with the K&N in there.

 

Thats whats got me going ...huh?? It would seem with more air ...the car would lean up and need to add fuel with the trims. So are we better off power wise..... to run the stock filter with perfect trims ....or a K&N that has the car pulling fuel ?