Gas cap on an 87 fj60 with a 3fe engine

[venturehunter]

My son just put a 3fe engine in my 87 fj60. We installed an electric fuel pump in front of the tank and now after I drive the cruiser a little while and remove the gas cap, there's quite a vacuum sound. I should mention that the first time I drove it, I went into the insurance office and when I came out it didn't want to start. Should I change to a vented gas cap?

Thanks,
Jim