[Gasoline Fumes]

Mine's in front of the grill. I'd be surprised if there was a difference in front versus behind. But in front of the grill is easier to install, easier to adjust and will be pushed towards the grill by air pressure. If it's behind the grill, the air pressure could push it away from the grill if it's not adequately secured, allowing air to get by it. Which might not be a bad thing. It's at highway speeds that I have to open up my grill block more.