I was under the impression that a Walbro would significantly affect AFR, but there was no effect on fuel trims, and at WOT, the car ran only about 1/4 pt richer. That tells me that the stock FPR can handle the Walbro no prob. BTW, if anyone is wondering, I can definitely hear the Walbro. Its more of a faint hum more than a whine. I can only really hear it when the car is idling at a stop. I suspect that it would be a little more quiet if I had used the factory isolation pad. The Walbro one is pretty thick and pushes the pump firmly against the pump housing creating a pretty firm sound path for the vibration to reach the gas tank and chassis. That's all I have to say about that.